Optical disc for which a sub-picture can be favorably superimposed on a main image, and a disc reproduction apparatus and a disc reproduction method for the disc

ABSTRACT

A multimedia optical disc for recording main video data which is composed of sets of frame data that is processed beforehand to enable display at an aspect ratio specified out of a plurality of aspect ratios. The disc has a stream area storing streams made up of the main video data and a plurality of sets of sub-picture data, with each set of sub-picture data including a set of tel-op data and a set of coordinate information showing a display position of the set of tel-op data. The disc also includes a control area storing a plurality of pairings of a set of display mode information and a set of sub-picture indicating information. Each set of display mode information shows a species of display method according to which the frame data is to be processed for a case when the frame data decoded from the main video data is displayed at one of the plurality of aspect ratios. Each set of sub-picture indicating information shows a set of sub-picture data, out of the plurality of sets of sub-picture data in a same stream as the main video data, which includes a set of coordinate information which coincides with the species of display method shown by the display mode information.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical disc on which an informationsignal is recorded, and to a reproduction apparatus for the opticaldisc. More specifically, it relates to an optical disc which is used forrecording video information which includes video data, audio data, andimage data, and to a reproduction apparatus for the disc.

2. Description of the Related Art

Video applications, such as movies, are one kind of application whichcan be achieved using optical discs, such as laser discs, and a suitablereproduction device. These video applications are usually referred to as"video titles".

As the supply of video titles becomes increasingly internationalized,"multilingual video titles" are starting to appear on the market. Here,the expression "multilingual" refers to the user being able to selectsubtitles for one out of a plurality of languages which are thenreproduced with the moving picture information. As one example, amultilingual video title aimed at the U.S. and European markets caninclude separate dubbing soundtracks and sub-picture information forEnglish subtitles, German subtitles, French subtitles, and Spanishsubtitles, so that users can watch a movie in their specified language.

One of the technologies which underpins the realization of "multilingualvideo titles" is the use of MPEG (Moving Pictures Experts Group) streamdata as format for the data stored on the disc. MPEG streams includevideo information which has been compressed at a high compression rateaccording to MPEG methods, and can also include multiple sub-picturechannels and multiple audio channels which are selectively reproduced.This is to say, "multilingual video titles" can be achieved by storingthe moving picture information as the video information, dubbingsoundtracks for each of the featured languages as the multiple channelsof audio information, and subtitles for each of the featured languagesas the multiple channels of sub-picture information.

Another of the technologies which underpins the realization of"multilingual video titles" is the use of a process called OSD(On-Screen Display) processing performed by the disc reproductionapparatus. Here, OSD processing refers to the decoding of the image dataincluded as sub-picture information and the mixing of the image datawith the moving picture on the display. This is to say, when the userselects the language he/she would like reproduced, the disc reproductionapparatus selects and reproduces the sub-picture information on one ofthe channels in accordance with the selected language, with thesub-picture information being reproduced together with the movingpicture. The image data used here for displaying subtitles is known as"tel-op" data.

The position at which the sub-picture information is superimposed ontothe moving pictures is decided by the title producer when developing thetitle. As a result, during reproduction the sub-picture information canbe positioned at the producer's desired position. Here, should theproducer indicate a display command for a coordinate position around thechest of one of the characters in the main image, the disc reproductionapparatus may respond to that command by displaying subtitles showingthe character's name which are superimposed over the chest area of thecharacter. Here, when a plurality of characters are concurrentlydisplayed, the subtitles for characters' names can be displayed atpositions corresponding to the respective characters, making suchsubtitles extremely effective.

Another recent trend in video titles, apart from the development of"multilingual titles", is the development of "wide-screen TV-adaptedtitles". Adaptation for wide-screen television refers to the developmentof titles which have a high visual impact when displayed on awide-screen television with an aspect ratio of 16:9, with the objectiveof giving commercially available video titles the same big-screenfeeling attained from watching movies at a movie theater.

One of the technologies underpinning the adaptation of titles forwide-screen TVs is, of course, the development of wide-screen TV sets.Wide-screen TV sets have a screen whose aspect ratio is 16:9 and performinterpolation for a NTSC (National Television System Committee) signalwhose image content has an aspect ratio of 4:3 to display an image whoseaspect ratio is 16:9. This is to say, video information which is storedon a disc is processed so as to squeeze its image content in thehorizontal direction to enable the information to be optimally displayedat a 16:9 aspect ratio. As described above, wide-screen TV sets performinterpolation for this video data which has been squeezed in thehorizontal direction and by doing so display the video information withan aspect ratio of 16:9.

Another of the technologies underpinning the adaptation of titles forwide-screen TVs is display mode transformation processing by discreproduction apparatuses. Here, display mode transformation processingrefers to image interpolation which enables a video title adapted to a16:9 aspect ratio to be reproduced by a conventional television setwhich has an aspect ratio of 4:3. As described above, video titles whichare adapted to wide-screen TV use are processed so as to give an optimaldisplay when displayed at an aspect ratio of 16:9. To do so, the videoinformation is shrunk in the horizontal direction. As a result,conventional TV sets which cannot perform horizontal interpolationduring display end up displaying the image shrunk in the horizontaldirection as it is. In order to perform compensation, display modetransformation processing is executed by disc reproduction apparatuses,and by switching the display format (display mode) of the image signalfor the main image, the image content can be arranged within the limiteddisplay area of a conventional TV set.

Here, "pan scan display mode" and "letterbox display mode" arerepresentative examples of display modes. In the former, pan scandisplay mode, video which is adapted to wide-screen television is slidby given distances in the vertical and horizontal directions inaccordance with the FCVO (Frame Center Vertical Offset) and the FCHO(Frame Center Horizontal Offset) which are standardized under MPEG,before the left and right edges of the image are trimmed to give animage which will fit onto a TV screen with an aspect ratio of 4:3.Putting this into other words, pan scan display mode involves acompensatory cutting of the image content of each frame so that theimage can be displayed on a TV screen with an aspect ratio of 4:3. Inthe latter, letterbox display mode, the image recorded with an aspectratio of 16:9 is reduced and displayed in the central area of a 4:3aspect ratio TV screen, with a corrective image being added above andbelow the central belt-like area where the image is displayed. Puttingthis in other words, letterbox display mode involves a compensatoryreduction of the image content of each frame with an aspect ratio of16:9 so that the image can be displayed on a TV screen with an aspectratio of 4:3.

When pan scan display mode and letterbox display mode are compared,letterbox display mode has the distinct merit of being an easier mode toachieve. This is because in pan scan display mode, the producer must setthe FCVO and FCHO values very carefully for each frame of video, so thatunintentional and undesired losses of image data, such as the trimmingof half a character's face, can be avoided.

Using the letterbox display mode and the pan scan display mode describedabove, video information which has been adapted for wide-screen TV canbe favorably arranged onto a conventional TV screen with an aspect ratioof 4:3. However, there remains the problem for TV sets, discreproduction apparatuses, and disc that when "multilingual video titles"which have been developed for wide-screen TV are displayed using theabove modes, the superimposing position of the subtitles cannot alwaysbe performed in accordance with the producer's intentions.

When a disc reproduction apparatus has a video title adapted forwide-screen TV displayed on a conventional TV with an aspect ratio of4:3, conversion to pan scan display mode is performed as describedabove, with this changing the position at which the video content isarranged. As a result, the sub-picture will end up being displaced fromthe desired position, which leads to a breakdown in the positionalcorrespondence between items on the screen and the subtitles related tothe items.

The following is a detailed explanation of the breakdown in thepositional relationship between a sub-picture and actual video footagewhich will refer to a specific example of video footage. Here, whenediting a video title which is a nature program, the producer wishes tosuperimpose subtitles onto a frame introducing bird life. Here, this oneframe of the wide-screen TV-adapted image is as shown by the referencenumeral y101 in FIG. 1A, with reference number y102 showing thesubtitles which are to be superimposed onto the frame. These subtitlesare to be superimposed at the feet of the bird in the image, with theproducer indicating that subtitles indicating the word "Penguin" are tobe superimposed at certain coordinates in the wide-screen TV-adaptedimage.

The combined image y103 shows the results of the superimposing of thesubtitles y102 on the image y101. Should the producer only see image,he/she should be satisfied with the results of the superimposing, sincein FIG. 1A the subtitles have been superimposed at the producer'sdesired position. Here, the results of the same superimposing for a mainimage displayed using pan scan mode are shown in FIG. 1B. From FIG. 1B,it can be clearly seen that the subtitles have been displaced from theintended position, since the superimposing has been performed with the"Penguin" subtitles at a position spatially defined with respect to thewide-screen TV-adapted image, despite the fact that the image has beentrimmed to fit the standard TV screen. This is because the coordinatesfor superimposing the sub-picture on the main video image in pan scandisplay mode are different to the coordinates for superimposing thesub-picture on the main video image in wide-screen TV-adapted mode.Here, the use of coordinates for an optimal superimposing position inwide-screen TV-adapted mode when displaying according to pan scandisplay mode can often result in the displacement of the display of thesub-picture.

FIG. 1C shows the combined image which results from the discreproduction apparatus switching to letterbox display mode. As can beseen, the "Penguin" subtitles once again end up displaced from theintended image content. This leftward displacement of the superimposingposition is caused, as was the case with the displacement in pan scandisplay mode, by the use of different coordinate systems. Here, the useof coordinates for an optimal superimposing position in wide-screenTV-adapted mode when displaying according to pan scan display mode canoften result in the displacement of the display of the sub-picture.

As shown in FIG. 1C, the subtitles end up being superimposed onto theborder between the main image and the corrective image, with the tophalf of the subtitles being displayed on the main image and the bottomhalf being displayed on the corrective image. As shown by theenlargement indicated by the arrow y104, since the subtitles aredisplayed in black, the favorable color contrast of the top half of thesubtitles is not achieved in the lower half.

Since the above displacement is due to the use of different displaymodes, it is possible to consider that the superimposing of thesub-picture on the main image would be better performed at a earlierstage of the process, which is to say before the conversion to pan scanor letterbox display. An example of when the main image and thesub-picture are combined before conversion into pan scan display mode isshown in FIG. 2A, with FIG. 2B showing the case when the main image andthe sub-picture are combined after conversion into letterbox displaymode. With the case shown in FIG. 2A, trimming the image for pan scandisplay mode results in the loss of the final two letters of "Penguin",while in FIG. 2B, reduction of the image for letterbox display moderesults in the reduction of the subtitles, so that the "e" and "g" of"Penguin" and end up appearing as if they have been colored in, makingthe letters very difficult to read.

While combining the main image and sub-picture at an early stage in thisway helps to overcome the problems of displacement, this improvement issurpassed by the loss of subtitles or by the difficulty of readingreduced characters, so that such methods cannot be consideredpracticable.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide a multimediaoptical disc and disc reproduction apparatus which can superimposesubtitles onto a main video image at the producer's desired position,for the display mode which is set for a television screen.

With the present construction, the multimedia optical disc storesinformation for selecting the sub-picture data in accordance with thepresent display mode, so that even when a video title is displayed on astandard TV with an aspect ratio of 4:3 in pan scan or letterbox mode,the subtitles will be superimposed at a position which is suitable forthe present display mode. By providing an area on a multimedia opticaldisc for storing information for selecting sub-picture information inaccordance with the display mode, the user becomes able to select adesired display mode while avoiding displacement of the subtitles on thetelevision screen. As a result, video titles which are unaffected bydisplay mode switching operations can be produced.

Here, the superimposing position of the sub-picture in the coordinatesystem for wide-screen television display mode may be set to protrudeinto the left or right edges of the screen which are trimmed in pan scandisplay mode, while the superimposing position of the sub-picture in thecoordinate system for pan scan display mode may be set so that thesubtitles do not protrude into the edges of the screen which are trimmedin pan scan display mode, and the superimposing position of thesub-picture in the coordinate system for letterbox display mode may beset so that the subtitles are superimposed over the corrective image.

Here, the multimedia optical disc is provided with information forselecting sub-picture data in accordance with a combination of a type ofdisplay mode and a logical channel number set in the disc reproductionapparatus. As a result, when a video title is reproduced using atelevision and the display is switched to pan scan or letterbox displaymode, the subtitles can be displayed at an optimal superimposingposition for the present display mode. By providing an area on amultimedia optical disc for storing information for selectingsub-picture information in accordance with the display mode and logicalchannel number, displacement of the subtitles can be avoided, and theproducer can decide the channel number allocation for different sets ofsub-picture data. As a result, video titles which are unaffected bydisplay mode switching operations can be produced.

On the other hand, when it is not necessary to take measures against theeffects of display switching operations, a same set of sub-picture datamay be commonly used in a plurality of display modes, so that it is notnecessary to provide a separate set of sub-picture data for everydisplay mode in every multiplexed stream in the stream area. Puttingthis into other words, the stream area can include sets of sub-picturedata which are unique to one display mode and sets of sub-picture datawhich are used in several display modes. Multiplexed streams in which aset of sub-picture data is used in several display modes have theadvantage of being of small data size, so that such streams will take upof smaller amount of the storage capacity of the multimedia opticaldisc.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, advantages and features of the invention willbecome apparent from the following description taken in conjunction withthe accompanying drawings which illustrate a specific embodiment of theinvention. In the drawings:

FIG. 1A shows the combining of a wide-screen TV-adapted main image and asub-picture;

FIG. 1B shows a combining of main image and sub-picture performed in panscan display mode;

FIG. 1C shows a combining of main image and sub-picture performed inletterbox display mode;

FIG. 2A shows a combined image displayed in pan scan display mode whencombining is performed at an early stage;

FIG. 2B shows a combined image displayed in letterbox display mode whencombining is performed at an early stage;

FIG. 3A shows the appearance of the optical disc used in the presentembodiment;

FIG. 3B shows a cross-section of the optical disc;

FIG. 3C shows an enlargement of the area around the focused spot of thelaser beam;

FIG. 3D shows sequences of pits in the information layer 109;

FIG. 4A shows the track arrangement of the information layer of theoptical disc;

FIG. 4B shows the physical sectors of the information layer of theoptical disc;

FIG. 5A shows the logical construction of the optical disc;

FIG. 5B shows the basic arrangement of the file layer and theapplication layer;

FIG. 6 shows an example of internal composition of video title set V1,video title set V2, and video title set V3;

FIG. 7 shows an example of the group of video materials which areincluded in video title set V1;

FIG. 8 shows the internal construction of VOB#1 which is included in thegroup of video materials of video title set V1;

FIG. 9 shows the content of VOBU#50 through VOBU#55;

FIG. 10A shows the internal composition of a video pack;

FIG. 10B shows the internal composition of an audio pack;

FIG. 10C shows the internal composition of a sub-picture pack;

FIG. 10D shows the internal composition of a management informationpack;

FIG. 11A shows the internal construction of sub-picture unit SP-0.55;

FIG. 11B shows the internal construction of sub-picture unit SP-1.55;

FIG. 11C shows the internal construction of sub-picture unit SP-2.55;

FIG. 11D shows the internal construction of sub-picture unit SP-6.55;

FIG. 11E shows the internal construction of sub-picture unit SP-12.55;

FIG. 11F shows the internal construction of sub-picture unit SP-15.55;

FIG. 12A shows an example of Japanese language subtitles which are usedin pan scan display mode;

FIG. 12B shows an example of Japanese language subtitles which are usedin letterbox display mode;

FIG. 12C shows an example of English language subtitles;

FIG. 13A shows the combining coordinates for subtitles which are used inpan scan display mode;

FIG. 13B shows the combining coordinates for subtitles which are used inletterbox display mode;

FIG. 13C shows the combining coordinates for subtitles which are used inwide-screen TV display mode;

FIG. 14 shows an example of the internal composition of the VTS internaltitle search pointer table;

FIG. 15 shows the internal composition of the PGC table in the VTSinternal title set management information;

FIG. 16A shows the format of the PGC information;

FIG. 16B shows the internal composition of the "VOB position informationtable";

FIG. 17 shows an example of the internal composition of the videomanager;

FIG. 18 shows an example of the volume menu;

FIG. 19 shows the viewing environment for a video title in the presentembodiment;

FIG. 20 shows the four display types of video titles;

FIG. 21 shows an example key arrangement for the remote controller 91;

FIG. 22A is a block diagram of the internal construction of the DVDplayer 1 of the present invention;

FIG. 22B is a block diagram showing the composition of the signalseparating unit 86;

FIG. 23 shows the internal construction of the system control unit 93;

FIGS. 24A through 24C are flowcharts showing the content of theprocessing executed by the system control unit 93;

FIGS. 25A and 25B are flowcharts showing the processing in the remotecontrol processing routine of the system control unit 93;

FIG. 26 is a flowchart showing the processing executed by thesub-picture decoder 88; and

FIGS. 27A to 27D show combined images which are used in the four typesof viewing environments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order to assist the reader's understanding, the following explanationhas been divided into items which have each been given an index number.Here, the number of digits in the index number indicates the level ofthe item in question in the overall structure of the explanation. Here,the highest-ranked classification numbers are (1) and (2) , with (1)relating to the optical disc and (2) relating to the reproduction device(disc player).

(1) Physical Construction of the Optical Disc

(1.1) Logical Construction of the Optical Disc

(1.1.1) Logical Construction . . . Video Title Set

(1.1.1.1) Video Title Set . . . Video Object (VOB)

(1.1.1.1.1) Each kind of pack multiplexed into a Video Object (VOB)

(1.1.1.1.2) Sub-picture unit formed by a Video Object (VOB)

(1.1.1.1.3) Video Object (VOB)--Management Information Pack

(1.1.1.2) Video Title Set--Video Title Set Management Information

(1.1.1.2.1) Video Title Set Management Information-PGC information

(1.1.2) Logical Construction--Video Manager

(2.1) Outline of the Disc Reproduction Device

(2.2) Construction Elements of the Disc Reproduction Device

(2.2.1) Disc Reproduction Device Construction of Signal Separating Unit86

(2.2.2) Disc Reproduction Device Construction of System Control Unit 93

(1) Physical Construction of the Optical Disc

A digital video disc (DVD) which has a diameter of 120 mm and has astorage capacity of 4.7 GB on one side is ideally suited for use as themultimedia optical disc of the present embodiment.

FIG. 3A shows the appearance of the optical disc, while FIG. 3B showsits cross-section and FIG. 3C shows an enlargement of the circled partof FIG. 3B. Starting from the bottom of this figure, DVD 107 is formedof a first transparent substrate 108, an information layer 109, abonding layer 110, a second transparent substrate 111 and a print layer112 for printing a label.

The first transparent substrate 108 and the second transparent substrate111 are reinforcing substrates which are made of a same material and arearound 0.6 mm thick. This is to say, both substrates are roughly 0.5mm-0.7 mm thick.

The bonding layer 110 is provided between the information layer 109 andthe second transparent substrate 111 to bond them together.

The information layer 109 includes a reflective membrane, such as metalfoil, which is attached to the first transparent substrate 108. Here, ahigh density of indented and protruding pits is formed in thisreflective membrane by a manufacturing process.

The shape of these pits is shown in FIG. 3D. As shown in FIG. 3D, thelength of the pits varies between 0.4 μm and 2.13 μm, with the pitsbeing aligned in a spiral with radial intervals of 0.74 μm between themto form one spiral track.

By shining the laser beam 113 on these pits and measuring the changes inthe reflection ratio of the light spot 114 shown in FIG. 3C, informationcan be retrieved from the disc.

The light spot 114 on a DVD has a diameter of around 1/1.6 times thediameter of a light spot on a conventional CD due to an increase in thenumerical aperture (NA) of the objective lens and a reduction in thewavelength λ of the laser beam.

DVDs of the physical construction described above can store around 4.7GB of information on one side, which is almost eight times the storagecapacity of a conventional CD. As a result, it is possible to achieve agreat improvement in picture quality for moving pictures and to increasethe reproduction time from the 74 minutes which is possible with a videoCD to over two hours.

The substrate technique which has enabled this improvement in storagecapacity is a reduction of the spot diameter D of the laser beam. Here,spot diameter D is given by the equation "D=laser wavelength λ/numericalaperture of objective lens NA", so that the spot diameter D can bereduced by reducing the laser wavelength λ and by increasing thenumerical aperture of objective lens NA. It should be noted here that ifthe numerical aperture of objective lens NA is increased, comaticaberration occurs due to the relative inclination, known as "tilt",between the optical axis of the beam and the disc surface. In order tosuppress this phenomenon, DVDs use a transparent substrate of reducedthickness. Such a reduction in the thickness of the transparentsubstrate creates the problem of reduced physical durability for thedisc, although this problem can be overcome by reinforcing DVDs withanother substrate.

Data is read from DVDs using an optical system with a short wavelength(650 nm) red semiconductor laser and an objective lens whose NA(numerical aperture) can be enlarged up to around 0.6 mm. If thethickness of the transparent substrate is reduced to around 0.6 mm, astorage capacity of up to 4.7 GB can be achieved for one side of a 120mm diameter optical disc.

FIG. 4A shows the arrangement when the spiral track is formed leadingfrom the inner periphery to the outer periphery of the information layer109, with a very large number of physical sectors being formed on thisspiral track in the direction for disc rotation. In the presentembodiments, a physical sector is an arc on the spiral track, and is thesmallest unit of data which can be reliably retrieved.

Each sector has the internal construction shown in FIG. 4B to ensure thereliability of data retrieval. As shown in FIG. 4B, each sector is madeup of a sector header area which is used to identify the respectivesector, a user data area for storing 2 Kbytes of data, and an errorcorrection code storage area which stores an error correction code forthe user data area in the same sector. When reading the user data areain the same sector, a disc reproduction device uses the error correctioncode to detect any errors in the sector, and performs error correctionwhen such errors are detected.

(1.1) Logical Construction of the Optical Disc

The following is an explanation of the logical construction of theoptical disc. This logical construction is made up of a three-layerhierarchy. The hierarchy is made up of a physical layer whose logicalconstruction is oriented towards the firmware of the disc reproductionapparatus, a file layer whose logical construction is designed for themanagement of a plurality of sectors in file units, and an applicationlayer which has a multi title logical construction. Here, the logicalconstruction of the physical layer is shown in FIG. 5A and the logicalconstructions of the file layer and the application layer are shown inFIG. 5B.

The following explanation will first deal with the physical layer whoselogical construction is oriented towards firmware. Here, firmware refersto the control program for controlling a mechanical construction whichincludes a spindle motor and an actuator for an optical pick-up. Inorder from the top of FIG. 4A, the logical format of the physical layeris composed of a lead-in area which has identification informationincluded in a sector address, a volume area and finally a lead-out area,so that on reading such areas, the firmware has the spindle motor andactuator of the optical pickup activated.

The lead-in area stores operation stabilization data and the like whichis used when the disc reproduction apparatus starts reading data fromthe optical disc. The lead-out area informs the reproduction device ofthe end of reproduction and does not store meaningful data.

The volume area is an area for storing many kinds of data, as well asfor managing the physical sectors to which the volume area belongs aslogical blocks. These logical blocks are identified by firmware usingserial numbers which are assigned to consecutive physical sectors, withthe first physical sector in the data recording area being assigned thenumber zero. The enlarged portion "301" of FIG. 5A shows a group oflogical blocks in the volume area. Here, the figures, #m, #m+1, #m+2 and#m+3 which are appended to the logical blocks in this circled area arethe logical block numbers.

The following is an explanation of the file layer and the applicationlayer. This file layer and application layer exist in the volume areashown in FIG. 5B.

The file layer is divided into a volume management area and a file area.The volume management area stores file system management informationwhich is used to manage a plurality of logical blocks as files, inaccordance with ISO 13346 Standard. The file system managementinformation shows the relations between the file names for a pluralityof files and addresses of the groups of logical blocks which contain thecorresponding files. This file system management information is used bythe disc reproduction device to access the disc in file units. Morespecifically, when accessing this area, the disc reproduction apparatusrefers to all the system management information to calculate all of thegroups of logical blocks for the desired file, before accessing thesegroups of logical blocks to fetch the desired digital data.

The following is an explanation of the logical construction of theapplication layer. The information in this application layer can be mostloosely classified into a Video Manager and a plurality of Video TitleSets. Here, a Video Title Set is a group of movie titles which areclassified from the viewpoint of common use of a same set of videomaterial, while the Video Manager is information for managing all of thegroups in the title sets as a single set. In the example shown in FIG.5B, the grouping of video materials included in Video Title Set V1 is acollection of images of mammals and birds shot on location on theAntarctic, while Video Title Set V2 is made up of images showinghistorical sites in South-East Asia which have been produced with thecooperation of the local governments. Using the video materials in VideoTitle Set V1, a plurality of video titles, namely "Wildlife in theAntarctic: a Pictorial Documentary", "Interactive Antarctic Adventure","A Fairy Tale of the Antarctic", and "Multimedia Guide to the Wildlifeof the Antarctic", can be provided to make full use of valuable scenesshot on location in the Antarctic.

Using the video materials included in Video Title Set V2, the titleproducer can have the viewer enjoy a documentary about the excavation ofhistorical sites, a multimedia guide to historical sites, an adventuregame where participants search for historical sites, or a quiz abouthistorical sites around the world. By making good use of the valuablevideo materials in this way, the producer can provide a plurality ofvideo titles to the user.

By classifying video titles in terms of usage of shared video materialsin this way, it is possible to have a plurality of titles with commonvideo materials grouped together.

(1.1.1) Logical Construction--Video Materials included in a Video TitleSet

Each video title set is made up of video title set managementinformation and a group of video materials. The following explanationwill first deal with the group of video materials included in a videotitle set. Normally, when a movie is recorded onto film or video tape,an editing process is performed whereby only the required scenes are cutfrom the master tape and are arranged into the order of the story. Whensuch scenes are recorded into a Video Title Set, however, no suchediting operations are performed. This is to say, there is no editingprocess in which only the necessary parts of the necessary scenes areextracted and arranged into the order of the story. In fact, a VideoTitle Set can store video materials in a completely random order withoutany extraction of necessary materials from the original footage. Thegroup of video materials which are stored in Video Title Set V1 areshown in FIG. 7. As shown in this figure, the Video Title Set V1 of FIG.7 includes a plurality of video objects (VOBs) which each have differentreproduction times. Here, the expression "VOB" refers to one set ofmultiplexed stream data that is made up of various kinds of stream data,such as video data, audio data, sub-picture data, and control data,which are of variable code length. Such multiplexed stream data isbetter known as an MPEG stream, and this is the unit that is used forrecording one scene on a DVD.

In FIG. 7, VOB#1 has a reproduction time of ten minutes, and is actualfootage of the habitat of the emperor penguin. VOB#2 has a reproductiontime of fifty seconds and is actual footage of an adult and childrazorback. VOB#3 has a reproduction time of eight minutes and is actualfootage of the breaking away of the Antarctic ice cap. VOB#4 has areproduction time of forty-eight seconds and is actual footage of theindentation of the Weddell sea. The footage in these VOBs is entirelyshot on location in the Antarctic.

(1.1.1.1) Composition of a Video Object (VOB)

FIG. 8 shows the internal composition of a VOB. As shown in the drawing,each VOB is made up of a sequence of a plurality of VOB units (VOBU)which has been arranged in a time series with the first VOBU to bereproduced at the front. Here, a VOBU is a multiplexed set of thevarious kinds of variable code length data, with each of the multiplexedpieces having a reproduction time between 0.5 and 1.0 seconds. Asexamples, VOBU#91 is a collection of the variable code length data whichis to be used for the reproduction for the time period of 00 min: 45.50sec to 00 min:46.00 sec after the reading of VOB#1 has commenced, whileVOBU#147 is a collection of the variable code length data which is to beused for the reproduction for the time period of 01 min: 13.50 sec to 01min:14.00 sec after the reading of VOB#1 has commenced.

The "variable code length data" which is described above as beingmultiplexed into a VOB can be video data, a plurality of channels ofaudio data, and a plurality of channels of sub-picture data, with piecesof such data which are multiplexed into a VOBU being respectively calledvideo packs, audio packs, and sub-picture packs, each of which is 2 KBin size.

While the VOB units in each VOB are arranged into a time series, eachpack in each VOB unit is arranged in an order which, with the exceptionof the provision of the management information pack at the front, iscompletely random in terms of number of packs and pack order. This is tosay, there can be VOB units which have the order audio data, sub-picturedata, video data, and other VOB units which have the order, sub-picturedata, video data, audio data. As other examples, there may also be VOBunits which are made up of three hundred or so packs of nothing butvideo data, and other VOB unit which are made up of five hundred or sopacks.

Here, the reason the order of the packs can be different for each VOBunit is that it is not necessary for packs of a same kind to be next toeach other when the variable code length data is fetched and buffered bya reproduction apparatus. The reason why there can be different numbersof video, audio and sub-picture packs in each VOBU is that these kindsof data are encoded with a variable coding length, so that there can belarge discrepancies in the amount of data which is necessary to achievereproduction for a 0.5 to 1.0 second period.

To achieve reproduction with the unit time at 0.5 seconds, it isnecessary to inform the disc reproduction apparatus before the start ofthe 0.5 second period whether it is sufficient to transfer only a smallamount of data, or whether a large amount of data is required, and tohave the decoder provided inside the disc reproduction apparatus performdecoding for the necessary amount of transferred data. Here, to havevariable code-length data reproduced with a uniform reproduction time of0.5 seconds, a management information pack is provided at the start ofeach set of VOB unit, with this management information pack indicatingthe transfer rate which is required for the reproduction of the VOB unitto which it belongs, as well as the transfer rate and buffer size whichare required by each of the video stream, the audio stream, and themanagement information stream in the VOB unit. To give a specificnumerical example, 0.5 seconds of video reproduction will generallyrequire several hundred video packs, with the reproduction device beinginformed of a necessary transfer rate in the region of 4.5 Mbit/secondbefore such number of packs are read from the DVD to enable the decodingof such number of video packs.

FIG. 9 shows the contents of VOBU#50 through VOBU#55, which are VOBunits for the 3.0 second reproduction period from the 25.00 secondreproduction mark of VOB#1 to the 28.00 reproduction mark.

VOBU#50 is the VOB unit which is used for the reproduction periodbetween the 00 hr:00 min:25.00 sec and the 00 hr:00 min:25.50 sec marksafter the commencement of the reading of VOB#1, while VOBU#51 is the VOBunit which is used for the reproduction period between the 00 hr:00min:25.50 sec and the 00 hr:00 min:26.00 sec marks after thecommencement of the reading of VOB#1. In the same way, VOBU#55 is theVOB unit which is used for the reproduction period between the 00 hr:00min:27.50 sec and the 00 hr:00 min:28.00 sec marks after thecommencement of the reading of VOB#1.

(1.1.1.1.1) Each kind of pack in a VOB unit (VOBU)

The following is an explanation of the content each VOBU with referenceto FIG. 9. As shown in the figure, VOB#50, which is reproduced betweenthe 00 hr:00 min:25.00 sec and the 00 hr:00 min:25.50 sec marks,includes the management information pack "NAVI-50", the video packs"video50.1" and "video50.2", and the audio packs "audio-0.55","audio-1.55", and "audio-3.55".

The management information pack "NAVI-50" informs the disc reproductionapparatus of the transfer rate and buffer size which are required by thereproduction of VOBU#50 between the 00 hr:00 min:25.00 sec and the 00hr:00 min:25.50 sec marks.

The video packs "video50.1" and "video50.2" are the video packs whichare used during the reproduction of VOBU#50. These video packs are twoof the first video packs which are used, out of the several hundredvideo packs reproduced during the reproduction of VOBU#50 between the 00hr:00 min:25.00 sec and the 00 hr:00 min:25.50 sec marks.

These video packs, such as "video50.1" and "video50.2", have thestandard data format which is shown in FIG. 10A. The video packs shownin the drawing are made up of a "pack header", a "packet header", and a"data field" which are standardized according to MPEG, and are each 2 KBin size. The "pack header" includes data called a "pack start code", a"system clock reference (SCR)", and a "multiplex (MUX) rate" which isstandardized under MPEG, while the "packet header" is made up of astream ID, a packet length, an STD (System Target Decoder) buffer scalesize, a PTS (Presentation Time Stamp), and a DTS (Decoding Time Stamp)which are similarly standardized under MPEG.

The stream ID in the "packet header" is set at "1110 0000" for a videopack, as shown below the packet header in FIG. 10A. This informationshows that the elementary stream forming this pack is a video stream.

The SCR and PTS of a video pack are used for the synchronization of thedecoding process with the decoding processes of audio packs andsub-picture packs. More specifically, the video decoder of the discreproduction apparatus is synchronized to a standard clock based on theSCR, and, having decoded the video data in the data field, waits for thestandard clock to reach the time specified by the PTS. Once this time isreached, the decoded video data is outputted to a television monitor. Bydelaying its output based on the time indicated by the PTS, the videodecoder can avoid synchronization errors with the sub-picture output andthe audio output.

The data field of the video packs stores data which is composed ofI-pictures (Intra-Pictures), P-pictures (Predicative pictures) andB-pictures (Bidirectionally predicative pictures) which are standardizedunder MPEG. These, I-pictures, P-pictures, and B-pictures are obtainedby encoding actual video footage. It should be noted here that in thevideo packs, "video50.1" and "video50.2", the signal component of thevideo signal is "squeezed" before coding is performed. Here, "squeezing"refers to compression of the image content in the horizontal direction.In this way, the video packs "video50.1", "video 50.2" represent videowhich has been adapted to wide-screen TV display mode.

The audio packs "audio-0.55", "audio-1.55" represent the audio datawhich is used when VOBU#55 is reproduced. The reproduction period ofVOBU#55 is from 00 hr:00 min:27.50 sec to 00 hr:00 min:28.00 sec, sothat in the present figure, the audio packs for a reproduction time of2.5 seconds further forward are stored in VOBU#50. The "0" and "1" usedin the reference numbers of audio packs "audio-0.55" and "audio-1.55"respectively show that these audio packs are used as the 0^(th) and the1^(st) substreams during the reproduction period of VOBU#55. Under MPEGstandards, the "n^(th) substream" refers to a n^(th) digital datasequence which is obtained by recombining the multichannel sub-picturedata and audio data for a classification known under MPEG as a "privatestream". Here, a "private stream" is one species of elementary stream,with an elementary stream being a general name for digital datasequences in which packs belonging to a VOB are combined according totype. Since it is not possible to make a clear distinction between audiodata and sub-picture data, substreams are provided in the logicalconstruction of DVDs to clarify the classification of sub-picture dataand audio data, so that by assigning fixed substream IDs to sub-picturedata and audio data, these classifications can be clearly established.

The audio packs described above share the standard data format which isshown in FIG. 10B. This format is fundamentally the same as that of avideo pack in that it contains a "pack header", a "packet header", and a"data field". The differences with a video pack lie in the setting ofthe stream ID at "1011 1101" in the packet header and in the setting ofthe substream ID in the first eight bits in the bits field, with thesebeing shaded in FIG. 10B. The setting of the stream ID at "1011 1101" inthe stream ID shows that the elementary stream formed by the pack inquestion is a private stream.

As with a video pack, the "pack header" of an audio pack includes data,such as a pack start code and an SCR which are standardized under MPEG.The "packet header", meanwhile, stores a stream ID, a packet length, anSTD buffer scale size, a PTS, and a DTS which are standardized underMPEG.

The SCR and PTS of an audio pack are used for synchronizationadjustments with respect to the decoding of video packs and sub-picturepacks. More specifically, the audio decoder of a disc reproductionapparatus is synchronized to a standard clock based on the SCR, and,having decoded the audio data in the data field, waits for the standardclock to reach the time specified by the PTS. Since the decoding ofaudio data has a much lighter load than the decoding of video data orsub-picture data, the output delay for audio data is somewhat longerthan those of video data and sub-picture data. Once the time indicatedby the PTS has been reached, the audio decoder outputs result of thedecoding to a speaker. By delaying its output based on the timeindicated by the PTS, the audio decoder can avoid synchronization errorswith the sub-picture output and the video output.

The "data field" of an audio pack stores digital audio according toLinear PGM or Dolby AC-3 methods.

For the example shown in FIG. 9, the audio packs used in VOBU#55 arestored in VOBU#50. This is possible because the disc reproductionapparatus can know from the PTS at what time audio data is to bereproduced. As a result, audio packs may be stored in VOBUs whosereproduction times are well in advance of a present VOBU without causingany operational problems.

The following is an explanation of the internal composition of VOBU#51shown in FIG. 9. As shown in FIG. 9, VOBU#51, which is reproducedbetween the 00 hr:00 min:25.50 sec and the 00 hr:00 min:26.00 sec marks,includes the management information pack "NAVI-51", the video packs"video51.1" and "video51.2", and the sub-picture packs "SP-0.55.1","SP-1.55.1", "SP-2.55.1", and "SP-15.55.1".

The management information pack "NAVI-51" informs the disc reproductionapparatus of the transfer rate and buffer size which are required by thereproduction of VOBU#51 between the 00 hr:00 min:25.50 sec and the 00hr:00 min:26.00 sec marks.

The sub-picture pack "SP-0.55.1" represents the sub-picture data whichis used when VOBU#55, whose reproduction period is from 00 hr:00min:27.50 sec to 00 hr:00 min:28.00 sec, is reproduced. The numeral "55"in the reference number "SP-0.55.1" shows that the present sub-picturepack is one of the sub-picture units which is used during thereproduction of VOBU#55. This means that packs for a reproduction timeof 2.0 seconds further forward are stored in VOBU#51. Here, asub-picture unit is the smallest unit of sub-picture information whichis can be subjected to OSD processing by the disc reproductionapparatus, and includes display commands and image data which is encodedaccording to run-length encoding.

The "1" in the reference number "SP-0.55.1" is a serial unit numberwhich is allocated to the sub-picture pack. Here, serial unit numbersare serial numbers which are assigned to a plurality of sub-picturepacks which compose one sub-picture unit, so that the setting of "1" insub-picture pack "SP-0.55.1" shows that this sub-picture pack is thefirst compositional element in the sub-picture unit for the reproductiontime of "VOBU#55".

The number "0" in the reference number "SP-0.55.1" shows the substreamID of the present sub-picture pack. Here, a substream ID is anidentifier showing to which of the 32 sub-picture substreams the presentsub-picture pack belongs. Naturally, the setting "0" for the presentsub-picture pack indicates that the present sub-picture pack is anelement of the sub-picture unit which is used as 0^(th) sub-picturesubstream.

In addition to "SP-0.55.1", the sub-picture packs "SP-0.55.2","SP-0.55.3", "SP-0.55.4", and "SP-0.55.5" are also present assub-picture packs which form the sub-picture unit for the 0^(th)substream for the reproduction time of VOBU#55 between the 00 hr:00min:27.50 sec and 00 hr:00 min:28.00 sec marks. These show the second,third, fourth, and fifth sub-picture packs which form the sub-pictureunit for the 0^(th) substream at the reproduction time of VOBU#55.Putting this another way, the sub-picture unit for the 0^(th) substreamwhich is used at the reproduction time of VOBU#55 is divided into fiveVOB units (VOBU#51 through VOBU#55) when recorded onto an optical disc.Here, the reason the sub-picture units used at a given reproduction timeare distributed among preceding VOB units is that the image data whichforms the major element of the sub-picture unit is of a large data size,so that if such data were to be read during the reproduction time ofVOBU#55 between the 00 hr:00 min:27.50 sec and 00 hr:00 min:28.00 secmarks, it would be necessary for the disc reproduction apparatus to reada large amount of data in a short period of time, which carries the riskof breakdown in the reading process. With this in mind, the sub-picturepacks which form a sub-picture unit are distributed among a plurality ofVOBUs to prevent the reading processes of the disc reproductionapparatus being concentrated at the reproduction time of data.

In the same way, the sub-picture packs "SP-1.55.1", "SP-1.55.2","SP-1.55.3", "SP-1.55.4", and "SP-1.55.5" are the sub-picture packswhich form the sub-picture unit for the 1^(st) substream for thereproduction time of VOBU#55. These show the first, second, third,fourth, and fifth sub-picture packs which form the sub-picture unit forthe 1^(st) substream at the reproduction time of VOBU#55. From this, itcan be seen that the sub-picture unit for the 1^(st) substream which isused at the reproduction time of VOBU#55 is divided into five VOB units(VOBU#51 through VOBU#55) when recorded onto an optical disc.

The sub-picture packs "SP-2.55.1", "SP-2.55.2", "SP-2.55.3","SP-2.55.4", and "SP-2.55.5" are the sub-picture packs which form thesub-picture unit for the 2^(nd) substream for the reproduction time ofVOBU#55. These show the first, second, third, fourth, and fifthsub-picture packs which form the sub-picture unit for the 2^(nd)substream at the reproduction lime of VOBU#55. From this, it can be seenthat the sub-picture unit for the 2^(nd) substream which is used at thereproduction time of VOBU#55 is divided into five VOB units (VOBU#51through VOBU#55) when recorded onto an optical disc.

As described above, the sub-picture units for VOBU#55 further include a6^(th), a 12^(th) and a 15^(th) substreams. Although not shown in thedrawing, they are also divided into sub-picture packs which aredistributed among a plurality of VOBUs which precede VOBU#55 in the timeseries.

The sub-picture packs introduced here share the standard format which isshown in FIG. 10C. As can be seen by comparing the formats shown inFIGS. 10B and 10C, the data construction of a sub-picture pack isfundamentally the same as that of an audio pack, with it comprising a"pack header", a "packet header", and a "data field", as well as havinga eight-bit substream ID at the front of the data field.

As with an audio pack, the "pack header" includes a pack start code andan SCR which are standardized under MPEG. The "packet header" includes astream ID, a packet length, an STD buffer scale size, an SCR, and a PTS,which are similarly standardized under MPEG.

The SCR and PTS of a sub-picture pack are used for synchronizationadjustments with respect to the decoding of video packs and audio packs.More specifically, the sub-picture decoder of a disc reproductionapparatus is synchronized to a standard clock based on the SCR, and,having decoded the audio data in the data field, waits for the standardclock to reach the time specified by the PTS.

The decoder waits for such time because of the large discrepancies inthe processing loads of the decoding process for run-length encodedsub-picture data, the decoding process for the video data which requiresinternal frame decoding/internal field decoding and other movementcompensating prediction, and the decoding process for audio data. Also,while the decoding of video data is necessary for each GOP (Group ofPictures), the decoding of subtitles need only be performed at intervalsof several seconds. When the time indicated by the SCR is reached, thesub-picture decoder outputs the decoded sub-picture signal to the TVmonitor. By delaying its output based on the time indicated by the PTS,the sub-picture decoder can avoid synchronization errors with the audiooutput and the video output.

As with an audio pack, the stream ID of the "packet header" of amanagement information pack is set at "1011 1101" indicating a privatestream, although the substream ID in the data field is set a differentvalue. The most significant three bits of the substream ID in amanagement information pack are set at "001", with this being shaded inFIG. 10C. The least significant five bits of the substream ID are usedfor an identification code which indicates one of the sub-picturesubstreams #0˜#31.

(1.1.1.1.2) Video Object--Internal Composition of a Sub-Picture Unit

FIG. 11A shows the composition of sub-picture unit 0.55 in the 0^(th)substream for the reproduction time of 00 hr:00 min:27.50 sec to 00hr:00 min:28.00 sec which is composed of the sub-picture packs 0.55.1 to0.55.5.

The sub-picture unit in the present figure includes the code sequence"RLE code sequence f1" that is obtained by subjecting image data torun-length encoding and a display command "(Xp1, Yp1), Widthp1 Heightp1"that informs the disc reproduction apparatus of the area on the TVscreen in which RLE code sequence f1 should be displayed. FIG. 12A showsan example of the image data which represents the Japanese word ""meaning "penguin". The "p" in "(Xp1, Yp1)" indicates that pan scandisplay mode is operational, so that sub-picture unit SP-0.55 includes adisplay command for optimizing the coordinates of the code sequence "RLEcode sequence f1" in pan scan display mode. Here, Widthp1 shows thehorizontal extent of the image data of FIG. 12A, while Heightp1 showsits vertical extent. FIG. 13A shows the area indicated by (Xp1, Yp1) to(Xp2, Yp2) in the frame displayed using VOBU#55. In this drawing, thearea corresponding to (Xp1, Yp1) to (Xp2, Yp2) in the main image iscolored black to prepare it for the superimposing of image data.

In the coordinate system for pan scan display mode, the area (Xp1, Yp1)to (Xp2, Yp2) has the superimposing position shifted slightly to theleft so that the character row does not protrude into the area of theimage which is trimmed. By shifting the superimposing coordinatesslightly to the left, the producer is able to prevent the sub-pictureprotruding into the trimmed region.

FIG. 11B shows the composition of the sub-picture unit 1.55 of the1^(st) substream which is composed of sub-picture packs 1.55.1 to 1.55.5for the reproduction time of 00 hr:00 min:27.50 sec to 00 hr:00min:28.00 sec.

As shown in FIG. 11B, the sub-picture units include the code sequence"RLE code sequence f11" which is obtained by subjecting the image datashown in FIG. 12B to run-length encoding. The difference between theimage data of FIG. 12A and that of FIG. 12B is that a larger pointsetting of wider-spaced font is used in the latter.

The sub-picture unit SP-1.55 includes a display command for optimizingthe display coordinates of code sequence "RLE code sequence f11" inletterbox display mode, with this command being "(Xb1, Yb1)˜(Xb2, Yb2),Widthb1, Heightb1". The "b" in "(Xbn, Ybn)" is indicative of letterboxdisplay mode, while "Widthb1" and "Heightb1" respectively express thehorizontal and vertical extent of the image data of FIG. 12B inletterbox display mode. FIG. 13B shows the area on the display which isindicated by the coordinates (Xb1, Yb1)˜(Xb2, Yb2) for the one frameimage which is displayed for VOBU#55. Here, RLE code sequence f11 hasits image data displayed on an area which has been colored white on topof the black corrective image. By having the superimposing position ofthe RLE code sequence f11 determined in this command, the producer canhave the sub-picture displayed at a position which does not coincidewith the main image in letterbox display mode.

FIG. 11C shows the composition of the sub-picture unit 2.55 of the2^(st) substream which is composed of sub-picture packs 2.55.1 to 2.55.5for the reproduction time of 00 hr:00 min:27.50 sec to 00 hr:00min:28.00 sec.

In this drawing, the code sequence "RLE code sequence f11" is obtainedby subjecting the image data shown in FIG. 12A for the same subtitles asthe sub-picture unit of the 0^(th) elementary stream to run-lengthencoding. The display command "(Xw1, Yw1)˜(Xw2, Yw2) Widthw1 , Heightw1"in this drawing informs a disc reproduction apparatus of the area on theTV screen where the code sequence "RLE code sequence f11" is to besuperimposed. Here, (Xw1, Yw1) are the coordinates in wide-screen TVdisplay mode for the standard position of the image data, with the "w"in "Xwn, Ywn" indicating that the coordinates are for wide-screen TVdisplay mode. As before, "Widthw1" and "Heightw1" respectively expressthe horizontal and vertical extent of the image data of FIG. 12A inwide-screen TV display mode. FIG. 13C shows the area on the displaywhich is indicated by the coordinates (Xw1, Yw1)˜(Xw2, Yw2) for the oneframe image which is displayed for VOBU#55. Here, RLE code sequence f11has its image data displayed in the indicated area which is firstcolored black. It can be seen from FIG. 13C that the superimposingposition in wide-screen TV display mode protrudes rightward into thearea which would be trimmed in pan scan display mode. In this way, thepresent sub-picture unit is able to arrange the subtitles so as to makethe most of the extended width of the screen in wide-screen TV displaymode.

From the above description, it can be seen that the sub-picture unitsfor the 0^(th), 1^(st), and 2^(nd) substreams which are set thereproduction time of VOBU#55 all include Japanese language subtitleswhich can be superimposed onto the main image at an optimal position forany of pan scan, letterbox, or wide-screen TV display modes.

FIGS. 11D, 11E, and 11F show the compositions of the sub-picture unitsof the 6^(th), 12^(th), and 15^(th) substreams which are each composedof sub-picture packs n.55.1 to n.55.5 (n being 6, 12, or 15) for thereproduction time of 00 hr:00 min:27.50 sec to 00 hr:00 min:28.00 sec.

The sub-picture units in the present figures include the code sequence"RLE code sequence f2" which is obtained by subjecting image data theimage data shown in FIG. 12C to run-length encoding. As shown in FIG.12C, this image data is for the English subtitles "Penguin". In FIG.11D, the coordinates (Xp3, Yp3)˜(Xp4, Yp4) indicate the superimposingposition for the English subtitles "Penguin" in pan scan display mode,while in FIG. 11E, the coordinates (Xb3, Yb3)˜(Xb4, Yb4) indicate thesuperimposing position for the English subtitles "Penguin" in letterboxdisplay mode, and in FIG. 11F, the coordinates (Xw3, Yw3)˜(Xw4, Yw4)indicate the superimposing position for the English subtitles "Penguin"in wide-screen TV display mode.

From the above description, it can be seen that the sub-picture unitsfor the 6^(th), 12^(th), and 15^(th) substreams which are set thereproduction time of VOBU#55 all include English language subtitleswhich can be superimposed onto a main image at an optimal position forany of pan scan, letterbox, or wide-screen TV display modes.

As can be seen from the above description, VOB#55 uses six substreams tooptimize the superimposing position, font and character pitch in each ofthe three display modes. It should be especially noted here that VOB#1which includes the VOB unit which is designed to display subtitles atthe feet of the penguin shown in the main image is an exceptional videoobject, with the vast majority of VOBs included in the video materialshaving only one or two sub-picture substreams. This is because themajority of VOBs will use a same superimposing position, font, andcharacter pitch in all three display modes which are namely, pan scandisplay mode, letterbox display mode, and wide-screen TV display mode.

On the other hand, there can of course be VOBs which have as many asfifteen substreams. These are VOBs which include subtitles for fivelanguages in the three display modes.

The number of substreams provided in each VOB does not need to be equaland consists of a smallest necessary number in the range of one tothirty-two. By only multiplexing substreams where necessary, the datasize of VOBs can be reduced, which leads to more efficient use of thestorage capacity of discs.

1.1.1.1.3) Video Object (VOB)--Management Information Pack

As described above, the management information packs "NAVI-50","NAVI-51", and "NAVI-52" shown in FIG. 9 are arranged at the front ofeach VOBU and are used to indicate the required transfer rate. Since amanagement information pack is stored at the front of each VOB unit,each management information pack is only opened in a buffer in the discreproduction apparatus for the 0.5 seconds while the video packs, audiopacks, and sub-picture packs in the first VOB unit are read andreproduced, before the management information pack in the next VOB unitis read. Once this 0.5 second period has expired, the next managementinformation pack is overwritten into the buffer. Since each managementinformation pack is only opened in the buffer during the reading of thevideo, audio, and sub-picture packs in the same VOB unit, in addition tothe transfer rate, control information which only applies to the presentVOB unit can be indicated to the disc reproduction apparatus for onlythe 0.5-1.0 second period for which the video, audio, and sub-picturepacks in the present VOB unit are reproduced.

FIG. 9 shows the data construction of the management information packs"NAVI-50", "NAVI-51", and "NAVI-52". While the video packs, audio packs,and sub-picture packs are each formed of one packet, the managementinformation packs are each formed of two packets. Of these, one packetis called a PCI packet (Presentation Control Information packet) whilethe other packet is called a DSI packet (Data Search Informationpacket). The data construction of a management information pack issomewhat different to that of a video packet or an audio packet in thatit is made up of a "pack header", a "system header", a "packet headerfor PCI packet", a "data field for PCI packet", a "packet header for DSIpacket" and a "data field for DSI packet".

The system header stores management information for the entire VOB unitwhich has this management information pack at the front, in accordancewith MPEG standards. It stores the overall necessary transfer rate andan indication of a transfer rate and buffer size for each of the videostream, the audio stream, and the sub-picture stream.

The stream IDs of the two packet headers in a management informationpack, as shown by the oblique shading in FIG. 9, are both set theidentification code "1011 1111" which indicates "private stream 2".

The PCI packet contains the Highlight Information which is used toperform reproduction control in accordance with cursor operations formenus and confirmation operations for items, when the sub-picture packis used to display a menu made up of a plurality of items. In thepresent embodiment, the Highlight Information includes color informationfor the colors to be used in the sub-picture display, as well asreproduction control information for reproduction control to beperformed in response to confirmation operations.

A representative example of such "reproduction control in response to aconfirmation operation" is a branch which switches reproduction from apresent reproduction route to another reproduction route. Here,switching of reproduction route is performed by having commands, named"Highlight commands", stored in the Highlight information correspondingto each item in a menu, and by having these commands executed when themanagement information pack is read by the disc reproduction apparatus.Since these commands which correspond to each item, which in turncorrespond to a confirmation operation, are executed selectively,reproduction routes can be switched in units of one set of PGCinformation. PGC information is described in more detail later in thisspecification.

A DSI packet stores information which is necessary for the reproductionof an MPEG stream from the present data position. Each DSI packet alsostores the addresses of the preceding and succeeding DSI packets, whichare referred to when special reproduction functions, such as fastforward, are performed.

This concludes the explanation of video objects (VOB), so that thefollowing explanation will deal with the composition of the Video TitleSet management information in the Video Title Set.

(1.1.1.2) Video Title Set--Video Title Set Management Information

The Video Title Set management information is a collection of controlinformation for reproducing video materials, which have not beensubjected to any editing processes and have not been arranged in orderof reproduction, so that they compose one video title.

In the present embodiment, a video title is an image production that isexpressed using (1) a Video Title Set number which is uniquely assignedto the title on the optical disc, (2) one or more sets of PGCinformation which show the route taken by the optical pickup in readingthe optical disc, and (3) video information which is successively readfrom the optical disc in accordance with the PGC information. Thesekinds of information are managed by the Video Title Set (VTS) managementinformation in each Video Title Set. An example of such Video Title Setmanagement information is shown in FIG. 6. As shown in FIG. 6, thisVideo Title Set management information is composed of a "VTS internaltitle search pointer table", a "PGC table", and "VTS internal aspectratio information".

The "aspect ratio information" informs the disc reproduction apparatuswhether the group of video materials in the video title set are to besubjected to wide-screen display processing before display. As describedabove, the video content of the group of video materials in video titleset V1 is squeezed before recording into VOBs, so that in view of thissqueezed state of the video content, the aspect ratio information of thevideo title set V1 is set at "11 bit", indicating the performance ofwide-screen display processing to the disc reproduction apparatus. Bylooking at the aspect ratio information of the other video title sets inthe present figure, it can be seen that "11 bit" is also set for videotitle set V2, while "00 bit" is set for video title set V3. Here, thesetting "00 bit" indicates to the disc reproduction apparatus thatwide-screen display processing is not to be performed for the set ofvideo materials included in video title set V3.

The "PGC table" stores a plurality of sets of PGC information. Asdescribed above, VOBs store images which have not been edited orarranged into reproduction order, so that it is necessary to providedisc reproduction apparatuses with information showing how the videoinformation is to be reproduced. This information is provided by thesets of PGC information which are stored in the PGC table, as shown inFIG. 6. In order to arrange the video materials to create a scenario,each set of PGC information specifies a retrieval order of VOBs andvarious supplementary control indications for the disc reproductionapparatus to be executed during the reproduction of the indicated VOBS.Examples of such supplementary control are control for the mapping ofsubstreams for the pairing of the logical channel number and the displaymode, or control to have branches performed between sets of PGCinformation.

The VOB reproduction orders in the various sets of PGC information inthe PGC table are expressed as lists of VOB position information. Here,the lists of position information included in sets of PGC informationare interpreted by a disc reproduction apparatus as retrieval orders forVOBs. In FIG. 8, the sets of PGC information each have their ownretrieval order of VOBs, which shows that a plurality of video titleswith different reproduction orders are prepared by rearranging the orderof the VOB position information in the different sets of PGCinformation. Putting this into other words, multiple scenarios arecreated using different arrangements of the same scenes.

Of special note here is that sets of PGC information in the PGC tableinclude link information for branches to other sets of PGC information,and that these links can be branch links in which a plurality of sets ofPGC information are linked to the present set of PGC information. Forbranch links, the branch destination is decided according to a useroperation during reproduction. Here, management information for managingall of the PGC information and information which is only valid for thePGC being reproduced are also stored in the PGC table, with an exampleof such being a color conversion table which is used for the sub-picturethroughout the entire reproduction period. This PGC managementinformation is not related to the gist of the present invention, and sowill not be described in detail. Instead, it should be noted that thesets of PGC information are provided for the retrieval of VOBs and forthe definition of supplementary control, with different sets of PGCinformation being used in the different scenarios for each video title.Since PGC information is used to describe scenarios, it is also known as"scenario information".

The "Video Title Set (VTS) internal title search pointer table is atable which is composed of title numbers, and pointers to sets of PGCinformation which correspond to VTS title search pointer #1, VTS titlesearch pointer #2, VTS title search pointer #3, etc. It is a table usedfor referencing the sets of PGC information stored in the PGC managementinformation table using a VTS internal title number. Here, a VTSinternal title number is a locale number for managing separate titles inthe Video Title Set.

FIG. 14 shows an example of the content of the VTS internal title searchpointer table. As shown in this figure, the VTS internal title searchpointers #1, #2, and #3 are respectively made up of a Video Title Setnumber and VTS internal title number (this pairing corresponding to thetitle number assigned to one of titles), and a number (PGC number) of aset of corresponding PGC information. The sets of PGC information whichare linked to the VTS internal title numbers in VTS internal titlesearch pointers #1, #2, and #3, are sets of PGC information which arespecified by a selection operation made by the user. These sets of PGCinformation are somewhat exceptional when compared to other PGCs, whichare stored without information showing the origins of branches, in thatthey are specified by a clear operation made by the user after referringto the available title names. As a result, these sets of PGC informationare appended with the label "Entry-PGC" to distinguish them from othersets of PGC information.

(1.1.1.2.1 Video Title Set Management Information--PGC Information

The following is an explanation of the data construction of the sets ofPGC information. Here, FIG. 16A shows the logical format of PGCinformation #1, #2, #3 . . . #6 in the PGC table, while FIG. 15 shows anexample of the kind of values which are set within this logical format.

As shown in FIG. 16A, each set of PGC information is made up of "PGClink information", "sub-picture mapping information", and a "VOBposition information table".

The VOB position information table uses sequences of VOB positioninformation to indicate to the disc reproduction apparatus what VOBsshould be read in what order for the present set of PGC information.Each set of VOB position information informs the disc reproductionapparatus of the storage position of each VOB on the optical disc, sothat the disc reproduction apparatus can have the optical pickup scanthat storage position. The content of the set of VOB positioninformation are shown in FIG. 16B. As shown in FIG. 16B, each set of VOBposition information in the present embodiment is expressed as a "VOBreproduction time", a "VOB offset", and a "No. of blocks in VOB". Whenreading a VOB, the disc reproduction apparatus uses the offset numbersincluded in the VOB position information and calculates the logicalblock numbers of the logical blocks in which the VOB is stored, beforehaving the optical pickup scan only the number of logical blocksindicated by the "No. of blocks" on the track of the optical disc.

The PGC link information is information which shows what reproductionroute continues after the present logical block. To do so, it storeslink destination information which shows what set of PGC informationshould be next read into the buffer. When the reproduction according toone set of PGC information is completed by the disc reproductionapparatus, the next set of PGC information is determined in accordancewith the "PGC link information", and this next set of PGC information isread from the disc and overwritten into the buffer. In this way, the PGCinformation is updated and reproduction control can continue inaccordance with the reproduction route indicated by this updated set ofPGC information. Here, for the example shown in FIG. 15, the linkdestination "PGC information#2" is given for PGC information#1, whilethe link destination "PGC information#3" is given for PGC information#2,and the link destination "PGC information#4" is given for PGCinformation#3. As a result, the disc reproduction apparatus can performreproduction control according to PGC information#2 having completed thereproduction control in accordance with PGC information#1, with PGCinformation#3 and #4 following on after this.

The sub-picture mapping information is information which indicates tothe disc reproduction apparatus the sub-picture substreams which can beused when performing reproduction control according to the PGCinformation and their selection conditions. The selection conditions ofeach substream are made up of logical channel numbers and display modeinformation.

Logical channel numbers are classification numbers which are assigned tosubstream IDs for the management of the display content of eachsubstream. As one example, the classifications referred to here can beEnglish subtitles, Japanese subtitles, and the like.

Display mode information is information which shows what processingshould be performed by the disc reproduction apparatus for each frame ofvideo information when the main image data is displayed in each of thedifferent display modes for the different aspect ratios.

The following is an explanation of a specific example composition of asubstream using the logical channel numbers and the display modeinformation. This example is shown in FIG. 15. In FIG. 15, the substreamID expressed as "0010 0001" in binary is the substream ID assigned tothe 1^(st) sub-picture substream. The information "CH0" and "aspectratio 4:3 letterbox" are given to the left of this substream ID, withthis line of information telling the disc reproduction apparatus todecode the sub-picture unit with the substream ID "0100 0001" when thelogical channel number in the disc reproduction apparatus is CH0 and thedisplay mode is "aspect ratio 4:3 letterbox". The line of informationwritten as "CH0", "aspect ratio 4:3 pan scan", "0100 0000", tells thedisc reproduction apparatus to decode the sub-picture unit with thesubstream ID "0100 0000" when the logical channel number in the discreproduction apparatus is CH0 and the display mode is aspect ratio 4:3pan scan.

In more detail, the information "aspect ratio 4:3 standard" shows thatthe viewer wishes to view an image title which has not been adapted foruse on a wide-screen TV on a conventional TV screen with an aspect ratioof 4:3. In the same way, the information "aspect ratio 16:9 standard"shows that the viewer wishes to view an image title which has beenadapted for use on a wide-screen TV on such a wide-screen TV screen withan aspect ratio of 16:9. The information "aspect ratio 4:3 pan scan"shows that the viewer wishes to view an image title which has beenadapted for use on a wide-screen TV on a conventional TV screen with anaspect ratio of 4:3 using a setting of pan scan display mode. Finally,the information "aspect ratio 4:3 letterbox" shows that the viewerwishes to view an image title which has been adapted for use on awide-screen TV on a conventional TV screen with an aspect ratio of 4:3using a setting of letterbox display mode.

In FIG. 15, PGC information #1 which defines the retrieval of VOB#1 hasthe 0^(th), 1^(st), 2^(nd), 6^(th), 12^(th), and 15^(th) sub-picturesubstream IDs set in the sub-picture mapping information. Since the0^(th), 1^(st), 2^(nd), 6^(th), 12^(th), and 15^(th) sub-picture unitsin VOB#1 have their own respective superimposing positions for thedifferent languages and display modes, the disc reproduction apparatuscan superimpose the sub-picture at an optimal position for the displaymode which is set for the TV screen in use.

PGC information #2 which defines the retrieval of VOB#2, on the otherhand, only has the 0^(th) and 15^(th) sub-picture substream IDs set inthe sub-picture mapping information. This is because although VOB#5assigns a substream to each logical channel number, the substreams forall three display modes use the same substream. Accordingly, for theperiod when PGC information #2 is valid, the disc reproduction apparatusmay select either of the 0^(th) and 15^(th) sub-picture units inaccordance with the value of the logical channel number. It is alsopossible here for other information to be included in the sets of PGCinformation, with a representative example of such being the "PGCcommand table".

The "PGC command table" is a table which stores various commands, suchas conditional branch commands which are appended to the "VOB positioninformation table". The disc reproduction apparatus executes thecommands which are written here before and after the retrieval of VOBsbased on the "VOB position information table", so that more dynamicswitching of reproduction routes can be achieved. The conditional branchcommands in the present table are expressed as comparisons to seewhether the values of general registers and immediate values are equalor higher/lower, with the branch destinations being expressed as PGCnumbers. Here, general registers are registers for storing values inaccordance with operations made by the user during reproduction, and areused to inform the disc reproduction apparatus of user operations whichhave been made using a remote controller or a control panel. Brancheswhich are performed in interactive software are performed using theseconditional branches which indicate sets of PGC information as theirbranch destinations.

(1.1.2) Logical Construction-Video Manager

The Video Manager is made up of VTS internal title search pointers,video objects, and sets of PGC information, with it being possible forits data construction to be standardized to that of the Video Title Set(although it should be obvious that it is far more simplified than thatof the Video Title Set). The difference between the VOBs for the VideoManager and the VOBs for the Video Title Set lies in the fact that theVideo Manager is used exclusively for reproducing the volume menu. Here,the expression "volume menu" refers to a menu in which all of the titlesstored on the optical disc are recorded, so that the user can select oneof the titles when the volume menu is displayed. When an optical disc isloaded into the disc reproduction apparatus, this volume menu isdisplayed on the screen immediately after the optical pickup has movedfrom the volume management area to the file area.

Since the Video Manager is only used for the volume menu, there are thefollowing two differences between the Video Manager and the Video TitleSet. Firstly, while the VOBs in the Video Title Set include video datafor actual footage, sub-picture data and audio data, the VOBs in theVideo Manager only contain a video pack, a sub-picture pack and amanagement information pack for a background image for a menu. Secondly,the branch destinations of the branch commands in the PGC informationand the management information of the Video Title Set, with certainexceptions, do not exceed the range of the Video Title Set, while thebranch commands in the Video Manager have branch addresses for titles ina variety of Video Title Sets on the optical disc, so that they cancross over between Video Title Sets.

The most significant characteristic of the Video Manager is that it isloaded into a memory provided in the disc reproduction apparatus for theduration that the optical disc is loaded in the disc reproductionapparatus. By having the Video Manager stored in memory in this way, thedisc reproduction apparatus can refer to the content of the VideoManager without performing a disc access operation.

FIG. 17 shows the data construction of the Video Manager. As shown inthis figure, the Video Manager is composed of "VOBs for menu", "PGC formenu", and a "VM internal title search pointer table".

The "VOBs for menu" are VOBs which are specially used for the volumemenu. As their name suggests, they include the sub-picture pack fordisplaying the volume menu and the management information pack forperforming reproduction control in accordance with cursor operations andconfirmation operations. The display image for a volume menu is shown inFIG. 18. The VOB for the volume menu includes a sub-picture pack inwhich character strings showing the titles have been subjected torun-length encoding, the titles including "1: Wildlife in the Antarctic:A Pictorial Documentary", "2: Interactive Antarctic Adventure", "3: AFairy Tale of the Antarctic", "4: Multimedia Guide to the Wildlife ofthe Antarctic", and "5: Exploring the Historic Sites of South-EastAsia". The user selects one of these title name character strings andperforms a confirmation operation to indicate the title to bereproduced. Here, the management information pack in the same VOBincludes a same number of sets of item information as there are titles.These sets of item information store a "Title Play" command whichindicates a branch to each title number and a "palette conversion range"which shows the area on the display whose color will change when thecorresponding item is in the selection condition.

The set of "PGC for menu" information is a set of PGC information whichis exclusively used for the volume menu, and stores the recordingposition of the corresponding menu VOB so that the menu VOB can be readwhen the optical disc is loaded into the disc reproduction apparatus.This set of PGC information is read by the disc reproduction apparatusimmediately after the disc has been loaded in the disc reproductionapparatus and the optical pickup has moved from the volume managementarea to the file area, and is used to guide the optical pickup so as toread the VOB for menu. In this way, the volume menu can quickly bedisplayed on the screen.

The VM internal title search pointer table is made up of a plurality ofVM internal title search pointers #1 . . . #69 which each correspond toa title number. In this figure, the VM internal title search pointer #1corresponds to title number 1, with VM internal title search pointers #2and #3 respectively corresponding to title numbers 2 and 3.

VM internal title search pointer #1 includes a pairing of a Video TitleSet number and a VTS internal title number. "Title No. 1" assigned tothe video title "1: Wildlife in the Antarctic: A Pictorial Documentary"corresponds to the VM internal title search pointer #1. In FIG. 17, theVM internal title search pointer #1 includes the VTS number indicatingVTS V1 and the first VTS internal title number. In the title searchpointer #1 in VTS V1 shown in FIG. 14, the VTS internal title number islinked to PGC information #5, showing that when the viewer selects thevideo title "1: Wildlife in the Antarctic: A Pictorial Documentary", theretrieval order of VOBs is given by PGC information #5 in VTS V1.

In the same way, "Title No. 3" assigned to the video title "3: A FairyTale of the Antarctic" corresponds to the VM internal title searchpointer #3. In FIG. 17, the VM internal title search pointer #3 includesthe VTS number indicating VTS V1 and the third VTS internal titlenumber. In the title search pointer #3 in VTS V1 shown in FIG. 14, theVT, internal title number is linked to PGC information #1, showing thatwhen the viewer selects the video title "3: A Fairy Tale of theAntarctic", the retrieval order of VOBs is given by PGC information #1in VTS V1.

(2.1) Outline of the Disc Reproduction Device

The following is an explanation of the disc reproduction apparatus ofthe present invention. The viewing setup for video titles, with anemphasis on a household audio-visual disc reproduction apparatus(hereafter referred to as a "DVD player"), is shown in FIG. 19. Theillustrated setup is composed of DVD player 1, a wide-screen TV monitor2, a standard TV monitor 3, and a remote controller 91.

DVD player 1 performs the reproduction of the video titles stored on anoptical disc. The reproduction of video titles by DVD player 1 consistsof the conversion of the VOB recorded on a DVD into an NTSC (NationalTelevision System Committee) or PAL (Phase Alternating by Line) signal.Such signals are standardized according to international televisionstandards, so that the conversion of VOBs to such signals enables thevideo titles recorded on a DVD to be reproduced by conventional TV setsin use around the world.

DVD player 1 has an opening in the front of its case and has a drivemechanism for driving a disc provided inside this opening.

A remote control receiving unit 92, which includes detecting elementsfor detecting the infra red signals emitted by the remote controller 91,is provided on the front of the DVD player 1, so that when the usermakes an operation with the remote controller 91 in his/her hand, theremote control receiving unit 92 generates an interrupt signal whichindicates the inputted key.

A video output terminal and an audio output terminal are provided on theback of the DVD player 1, so that when these terminals are connected toa standard TV set, a video signal (in NTSC or PAL format) read from aDVD can be enjoyed by the user.

In the present embodiment, both the wide-screen TV monitor 2 and thestandard TV monitor 3 are TV sets which display the signal outputted bythe DVD player 1. The difference between these TV monitors lies in theiraspect ratios, with wide-screen TV monitor 2 having an aspect ratio of16:9 and standard TV monitor 3 having an aspect ratio of 4:3. Since theaspect ratio of standard TV monitor 3 is 4:3, the video content can bearranged on the screen according to letterbox display mode or pan scandisplay mode.

As mentioned in the description of the construction of the multimediaoptical disc, of the titles recorded on DVD 107, video title sets V1 andV2 are adapted for display on a wide-screen TV, while video title set V3is not adapted for such display.

In the present system, there are four possible viewing environments forthe display for video titles, based on the differences in the displaymodes of the TV sets and whether or not the video titles have beenadapted for wide-screen TV display. These four possible viewingenvironments are shown in FIG. 20. These consist of a first type inwhich a video title which has been adapted to wide-screen TV display(such as video title which uses the video materials in video title setV1 or V2) is displayed on a TV monitor which has an aspect ratio of16:9, a second type in which a video title which has been adapted towide-screen TV display is displayed on a TV monitor which has an aspectratio of 4:3 using letterbox display mode, a third type in which a videotitle which has been adapted to wide-screen TV display is displayed on aTV monitor which has an aspect ratio of 4:3 using pan scan display mode,and a fourth type in which a video title which has not been adapted towide-screen TV display is displayed on a TV monitor which has an aspectratio of 4:3, with DVD player 1 performing control to select one ofthese environments as the present viewing environment. Display modeinformation is information for managing these modes, which can each beset its own value. These four values can be expressed in binary as "00","01", "10", and "11", corresponding to "aspect ratio 4:3", "aspect ratio16:9", "letterbox display mode", and "pan scan display mode". Inaddition to receiving user settings of the display mode value, the DVDplayer 1 also manages this value. This receiving of a user setting ofthe display mode value enables the DVD player 1 to know the user'sdesired viewing environment for a video title, and on receiving such asetting, the DVD player 1 stores the display mode value corresponding tothe chosen type of viewing environment so that it can control theviewing environment based on this value.

The remote controller 91 is used to receive user operations. An examplekey arrangement for remote controller 91 is shown in FIG. 21. As shownin FIG. 21, the ten key 911 is for numerical input which is made iscombination with other keys. The cross-shaped cursor keys 912 are forreceiving cursor operations. The "Enter" key is for confirmingselection. The "Switch audio channel" key 913 is for cyclically changingthe audio logical channel number. Here, "cyclically changing" refers tothe incrementing of the value until a maximum value is reached, afterwhich the value returns to zero. For the example when there are eightchannels, successive presses of a switch channel key result in theincrementing of the channel number in "0", "1", "2", "3", "4", "5", "6","7", "0", "1", "2", "3", "4", "5", "6", "7" order to select one channelin the range "0" to "7". The "Switch sub-picture channel" key 914 is forcyclically changing the sub-picture logical channel number. Finally, the"Switch display mode" key 915 is for cyclically changing the displaymode value.

(2.2) Construction Elements of the Disc Reproduction Device

FIG. 22A is a block diagram showing the construction of the DVD playerused in the present embodiment. The DVD player includes a drivemechanism 16, an optical pickup, a mechanism control unit 83, a signalprocessing unit 84, an AV decoding unit 85, a remote control receivingunit 92, and a system control unit 93. AV decoding unit 85 comprises asignal separating unit 86, a video decoder 87, a sub-picture decoder 88,audio decoder 89, a picture mixing unit 90, and a pan scan/letterboxconversion unit 95.

The remote control receiving unit 92 receives a key signal which isinfra red transmitted when a key on the remote controller 91 is pressed,and generates in interrupt signal indicative of the pressed key tonotify the system control unit 93 of the pressed key as a "receptioninstruction". Here, the kinds of reception instructions which can beused to notify the system control unit 93 include start reproductioninstructions, stop reproduction instructions, button selectioninstructions, button confirmation instructions, display mode switchinginstructions, sub-picture switching instructions, and audio switchinginstructions.

The drive mechanism 16 comprises a platter on which an optical disc isplaced and spindle motor 81 for rotating the inserted optical disc. Theplatter can be moved in and out of the DVD player by means of an ejectmechanism which is not shown in the drawing. The user places an opticaldisc on the platter when it has been projected forward outside the DVDplayer. After this, the platter is moved back into the DVD player toload the optical disc.

The mechanism control unit 83 controls the spindle motor 81 for rotatingthe disc and the mechanism made up of the optical pickup for reading thesignal from the disc and actuator 82 of the optical pickup. Morespecifically, the mechanism control unit 83 adjusts the motor speedaccording to a track position specified by system control unit 93. Atthe same time, it moves the optical pickup by controlling the actuator82 of the pickup and, having detected a correct track by servo control,waits until a desired physical sector is reached before continuouslyreading signals starting from desired position.

The signal processing unit 84 converts the signals read using theoptical pickup into a sequence of digital data while performing variousprocesses such as amplification, waveform shaping, conversion to binary,demodulation, and error correction. It then stores the processed data ina buffer memory inside the system control unit 93 in logical blockunits.

The AV decoding unit 85 applies certain processes to the digital datainputted as VOBs and converts the digital data into video signals andaudio signals.

The signal separating unit 86 receives the digital data transferred fromthe buffer memory in units of logical blocks (packets), and classifiesthe data into packs of management information data, video data,sub-picture data, or audio data by identifying the stream ID andsub-stream ID of each packet. The signal separating unit 86 outputsvideo data to the video decoder 87, audio data to the audio data decoder89, and sub-picture data to the sub-picture decoder 88. The signalseparating unit 86 also outputs management information packs to thesystem control unit 93. When such data is outputted, the system controlunit 93 indicates numbers to the signal separating unit 86, with, asshown in FIG. 6, these numbers indicating one set of audio data and oneset of sub-picture data. On receiving these indications from the systemcontrol unit 93, the signal separating unit 86 outputs only the data onthe specified channels to the audio decoder 89 and the sub-picturedecoder 89. The data on the other channels is discarded.

(2.2.1) Disc Reproduction Device--Construction of Signal Separating Unit86

FIG. 22B is a block diagram showing the construction of the signalseparating unit 86. As shown in the drawing, the signal separating unit86 comprises an MPEG decoder 120, a sub-picture/audio separating unit121, a sub-picture selecting unit 122, and an audio selecting unit 123.

The MPEG decoder 120 determines the types of packs transferred from thebuffer memory by checking the stream IDs and outputting the packets asfollows. If the stream ID is "1110 0000", the MPEG decoder 120 outputsthe packet to the video decoder 87. If the stream ID is "1011 1101", theMPEG decoder outputs the packet to the sub-picture/audio separating unit121. Alternatively, if the stream ID is "1011 1111", the MPEG decoder120 outputs the packet to the system control unit 93.

The sub-picture/audio separating unit 121 outputs the packets input fromthe MPEG decoder 120 to the sub-picture selecting unit 122 if theirsub-stream ID is "001* **** or to the audio selecting unit 123 if theirsub-stream ID is "1010 0***" or "1000 0***". As a result, each set ofsub-picture data and audio data is appropriately output to either thesub-picture selecting unit 122 or the audio selecting unit 123.

The sub-picture selecting unit 122 performs the selection processing forthe sub-picture packs sent from the sub-picture/audio separating unit121. As mentioned above, up to 32 sub-picture substreams can be includedin a VOB, but when English subtitles, for example, are indicated by thesystem control unit 93, the sub-picture selecting unit 122 will onlyoutput the sub-picture packs with the substream ID corresponding toEnglish subtitles to the sub-picture decoder 88 and will discard therest of the sub-picture packs which do not have the correspondingsubstream ID. As a result, the sub-picture decoder 88 will decode onlythe English subtitles.

The audio selecting unit 123 performs the selection processing for theaudio packs sent from the sub-picture/audio separating unit 121. Theaudio selecting unit 123 outputs only the audio data corresponding tothe indication from the system control unit 93 to the audio decoder 89and discards the rest of the audio data which does not have thecorresponding substream ID. As one example, when English, French, andJapanese dubbing soundtracks are available and the English dubbingsoundtrack is selected by the system control unit 93, the audioselecting unit 123 only outputs the audio packs for the English dubbingsoundtrack to the audio decoder 89, with the remaining audio packs beingdiscarded. As a result, the audio decoder 89 decodes only the Englishdubbing soundtrack.

The video decoder 87 decodes and decompresses the video data sent fromthe signal separating unit 86, before outputting the data to the picturemixing unit 90 as a digital video signal.

The sub-picture decoder 88 includes a buffer for storing a plurality ofsub-picture packs sent from the signal separating unit 86, and obtainssub-picture units by combining the sub-picture packs stored in thisbuffer.

FIG. 26 is a flowchart for the combining process of sub-picture packs.In step S1, the variable i is initialized. This variable i is used toindicate each of the sub-picture packs which are stored in the buffer inthe sub-picture decoder 88 and which form part of a sub-picture unit. Instep S2, the sub-picture selecting unit 122 refers to the substream ID(shown as the substream ID "inPACK" in the figure) of the sub-picturepacks which are inputted for storage in the buffer, and determineswhether this substream ID coincides with the substream ID indicated bythe system control unit 93. The substream ID indicated by the systemcontrol unit 93 is standardized according to the logical channel number(CHx) and the display mode number (MODx), and so is referred to as thesubstream ID (CHx, MODx).

If the substream IDs do not coincide, the sub-picture selecting unit 122discards the present sub-picture pack and the processing returns to stepS2, where the sub-picture selecting unit 122 waits for the input of thenext sub-picture pack.

If the substream IDs coincide, in step S3 the sub-picture selecting unit122 stores the present sub-picture pack, sub-picture pack (inPACK), asthe first element of the sub-picture unit (in buffer i!) (where i=1) inthe buffer. In step S4, the SCR and the PTS in the header of thesub-picture pack (in buffer i!) are decoded and are compared to thepresent time to see if they coincide. This check is performed sincethere is the possibility that the decoding time for a sub-picture unitalready stored in the buffer will have been reached while the storage ofsub-picture packs is repeatedly performed according to the processdescribed above.

If the decoding time has not been reached, the variable i is incrementedin step S5 and the processing returns to step S2, where the sub-pictureselecting unit 122 waits for the input of the next sub-picture pack.

In the next iterations of the processing in steps S2 to S5, thesub-picture units (in buffer i!) (where i=2, 3, 4, 5) are successivelystored in the buffer as the 2^(nd), 3^(rd), 4^(th), and 5^(th) elementsin the sub-picture unit.

Once the decoding time of the sub-picture unit is reached, in step S6the RLE code sequence in the sub-picture unit (in buffer) is expandedinto image data and is outputted to the image mixing unit 90, with, atthe same time, the display command (in buffer i!) of the sub-pictureunit being read from the first address in the sub-picture unit (inbuffer) also being outputted to the image mixing unit 90.

Here, if the image data is made up of a plurality of items and the usermakes a cursor operation for these items, the system control unit 93give an indication (called a "color change indication") for a change inthe indicated color of the image data to the sub-picture decoder 88.Since such color change indications are performed based on the itemcolor number in the Highlight information, items are changed to theselection color or confirmation color in accordance with this colorchange indication. By changing the colors of items, the displayed cursorcan be moved between the items. Here, the image mixing unit 90 isinformed of the coloring position and coloring range of the image dataindicated by the display commands in the sub-picture unit.

The following explanation will deal once again with the internalconstruction of the DVD player shown in FIG. 22A. The audio decoder 89decodes and expands the audio data inputted from the signal separatingunit 86 and outputs the result as a digital audio signal.

The pan scan/letterbox conversion unit 95 performs pan scan conversionor letterbox conversion of the video signal inputted from the videodecoder in accordance with the display mode indication from the systemcontrol unit 93. Here, if the set display mode is wide-screen TV displaymode or 4:3 aspect ratio display mode, the inputted video data isoutputted without processing.

When the indicated display mode is pan scan display mode, the left andright edges of the video data are trimmed to convert the video data to apan scan image. Alternatively, when the indicated display mode isletterbox display mode, the image is reduced in the vertical directionand corrective images are added above and below the image to convert thevideo data to a letterbox image.

The picture mixing unit 90 outputs a video signal after mixing theoutputs from video decoder 87 and sub-picture decoder 88 according tothe mixing ratio specified by system control unit 93. In order toperform image mixing, the image mixing unit 90 is provided with a planebuffer, with the image data expanded by the sub-picture decoder 88 beingarranged in the plane buffer into the superimposing position indicatedby the display command. As described above, this superimposing positionis set by the sub-picture decoder 88 decoding the display command in thesub-picture unit. After the image data is positioned, the content of theplane buffer is mixed with the video signal outputted by the panscan/letterbox conversion unit 95. The mixing ratio used here is setbased on the contrast written in the PCI packet in the managementinformation pack, with it being possible to change the mixing ratio foreach GOP. The mixed signal is then converted into a video signal forNTSC format and is then outputted to the TV monitor.

The system control unit 93 controls the entire disc reproductionapparatus and is provided with a program memory for storing a programfor achieving the functions of the system control unit 93, a work memorywhich is necessary for executing the program, a buffer memory forstoring the data in the logical blocks read from the disc, a CPU(Central Processing Unit) for executing the program, and an interfacecontrol unit for handling the input and output of control signals and ofdata to and from the periphery.

(2.2.2) Disc Reproduction Device--Construction System Control Unit 93

The following is an explanation of the internal construction of thesystem control unit 93 which is shown in FIG. 23. As shown in thefigure, the system control unit 93 is made up of a remote control inputinterpreting unit 71, a reproduction control unit 72, a button controlunit 73, a command interpreting/executing unit 74, a PGC informationbuffer 75, a buffer memory 76, and a system state management unit 750.

The remote controller input interpreting unit 71 interprets the remotecontrol key data received by the remote control receiving unit 92. Thisinterpreted remote control key data can be button selection instruction,a button confirmation instruction, a menu call instruction, an audioswitching instruction, a sub-picture switching instruction, a displaymode switching instruction, a start reproduction instruction, or a stopreproduction instruction. Of these, button selection instructions andbutton confirmation instructions are outputted to the button controlunit 73, while start reproduction instructions and stop reproductioninstructions are outputted to the reproduction control unit 72. Audioswitching instructions, sub-picture switching instructions, and displaymode switching instructions are outputted to the system state managementunit 750.

The button control unit 73 stores the management information pack of theVOB currently being reproduced which it receives from the AV decoderunit 85, and, when a button selection instruction and a buttonconfirmation instruction are received from the remote controller inputinterpreting unit 71, outputs a control signal to the AV decoder unit 85for changing the color of the sub-picture in a screen area assigned tothe button to the confirmation color, in accordance with the Highlightinformation in the PCI packet of the stored management information pack.Also, when a button confirmation instruction is received, it sends thecommand assigned to the selected button to the commandinterpreting/executing unit 74.

The command interpreting/executing unit 74 interprets the commandinputted from the button control unit 73 and, if there is a change ofPGC information which changes the reproduction route, the commandinterpreting/executing unit 74 outputs a reproduction controlinstruction notifying the reproduction control unit 72 of the new PGCinformation. The command interpreting/executing unit 74 also outputs asystem state control instruction notifying the system state managementunit 750 of when there has been a change to the state parameters storedinside the system.

The PGC information buffer 75 stores the current PGC information whichis used by the DVD player during reproduction, out of all the sets ofPGC information included in the PGC table.

The buffer memory 76 is used for storing the data which has beensubjected to the various processes such as amplification, waveformshaping, conversion to binary, demodulation, and error correction. Ifthe data written into the buffer memory 76 is Video Title Set managementinformation, it is written into another buffer which is not illustrated.On the other hand, if the data is a VOB, the system control unit 93transfers the data one pack at a time to the signal separating unit 86.When VOBs are transferred in this way, the management information packswill be sent back from the AV decoder unit 85.

The system state management unit 750 includes a group of state registerswhich is made up of various kinds of registers showing the present stateof the disc reproduction apparatus. These registers are the title numberregister 751, the PGC number register 752, the audio channel register753, the sub-picture channel register 754, and the video attributeregister 755.

The title number register 751 stores the title number of the titleselected for reproduction.

The PGC number register 752 stores the number of the PGC informationwhich is being used in the retrieval of the present VOB, out of all ofthe PGC information included in the video title whose number is storedby the title number register 751.

The audio channel number register 753 stores the number of the audiochannel which is presently valid, and outputs a control signal informingthe AV decoder 85 of the audio channel which is to be reproduced.

The sub-picture channel number register 754 stores the number of thesub-picture channel which is presently valid, and outputs a controlsignal informing the AV decoder 85 of the sub-picture channel which isto be reproduced. The logical channel number stored by this register ishereinafter referred to as the sub-picture channel CHx.

The video attribute register 755 stores the aspect ratio information inthe VTS management information in its higher-order bits and the displaymode number showing the present display mode of the TV monitor in itslower-order bits. If the aspect ratio information stored by thehigher-order bits is "16:9", the display mode information can becyclically changed so as to be one of "standard display mode", "pan scandisplay mode", and "letterbox display mode". If the aspect ratioinformation stored by the higher-order bits is "4:3", the display modeinformation is fixed at "standard display mode".

The reproduction control unit 72 receives reproduction startinstructions, reproduction stop instructions, and menu callinstructions, and performs predetermined control operations.

FIGS. 24A to 24C and 25A and 25B are flowcharts showing the processingperformed by the system control unit 93. These flowcharts will bereferred to in the following explanation of the operation of DVD player1.

When the user presses the eject button on DVD player 1, the platter ismoved outside the cover. After the user places an optical disc on thisplatter, the platter is moved back into the DVD player 1 to load thedisc. As shown in step S121 of FIG. 24A, the system control unit 93first waits for a disc to be inserted, and, on detecting that a disc hasbeen loaded using an optical sensor or the like, controls the mechanismcontrol unit 83 and the signal processing unit 84 to perform rotationcontrol with the optical pickup positioned in the lead-in region. Thisoperation continues until stabilized rotation has been achieved, atwhich point the optical pickup is moved outward from the lead-in regionto read the volume management area. Based on the information in thisvolume management area, the video manager is written into a buffer (stepS122). The system control unit 93 also calculates the storage address ofthe PGC information for the volume menu, and writes the PGC informationinto the PGC information buffer 75 (step S123). Since this PGCinformation is for the volume menu, it is stored in the buffer so thatthe system control unit 93 can refer to its content and calculate thestorage address of the VOBs to be reproduced for the menu. Once the VOBto be reproduced is decided, the system control unit 93 outputs acontrol signal to the mechanism control unit 83 and to the signalcontrol unit 84 and has the determined VOBs read from the optical disc.As a result, a volume menu, such as that shown in FIG. 18, is displayedon the TV monitor 2 (step S124). While this volume menu is displayed,the reproduction control unit 72 waits for the selection of a titlenumber (step S125).

Here, the user views the list of titles and confirms a selection ofhis/her desired title number. The selected title number is displayed,and the Highlight command, "PlayTitle", which is stored corresponding tothe selected title number, is read. Following this, in step S127 the VTSnumber #i and the VTS internal title number #j are read from the titlesearch pointer #k corresponding to the title number #k indicated by theoperands of the "PlayTitle" command.

Next, in step S131 of FIG. 24B, the aspect ratio information included inthe VTS management information for VTS#i is read and in step S132, it isdetermined whether the read aspect ratio information is 16:9. If this isnot the case, such as for VTS V3 which has an aspect ratio of 4:3, theprocessing advances to S144. If the read aspect ratio is 16:9, theprocessing advances to S133 where the initial value of the display modeMODx is read from the video attribute register 755, before theprocessing advances to the determination in step S138. In step S138, thesystem determines whether the display mode MODx is pan scan displaymode, and if so, the processing advances to step S139 where the panscan/letterbox conversion unit 95 is informed of pan scan display mode,before the processing advances to step S144.

If, in step S138, the read display mode MODx is not pan scan displaymode, the processing advances to step S140, where the system determineswhether the display mode MODx is letterbox display mode. If so, theprocessing advances to step S141 where the pan scan/letterbox conversionunit 95 is informed of letterbox display mode, before the processingadvances to step S144.

In step S144, the title number#j and the number of the Entry-PGCinformation are read from the title search pointer of VTS#i indicated byVTS number#i and are respectively written into the title number register751 and the PGC number register 752. After this, the route processingroutine is called in step S145 with the read PGC information#k as theEntry-PGC information.

FIG. 24C is the flowchart for the route processing routine. In thisfigure, the "VOB pointer" indicates the VOB to be read, out of the VOBposition information in the PGC information stored in the PGCinformation buffer 75, while the "block pointer" indicates the logicalblock which is presently being read, out of the VOB indicated by the VOBpointer.

In step S161, the logical channel number CHx stored in the sub-picturechannel register 754 is read, and the display mode number stored in thevideo attribute register 755 is read. In step S162, the sub-picturesubstream which has a substream ID that coincides with the combination(CHx, MODx) of the numbers read in step S161 is determined out of the 32substreams which can be included in the VOB. This is determined byreferring to the sub-picture mapping information of PGC information#kwhich is stored in the PGC information buffer 75. When the combinednumber (CHx, MODx) is mapped onto one of the substream IDs, only thesubstream packs with this substream ID (hereinafter referred to asubstream ID (CHx, MODx) are decoded in step S163, with the sub-pictureselecting unit 122 and the sub-picture decoder 88 being instructedbeforehand to discard sub-picture packs with other substream IDs.

Once these indications have been sent to the sub-picture selecting unit122 and the sub-picture decoder 88, the processing advances to S164where the system control unit 93 initializes the VOB pointer by settingthe first VOB in the VOB position information table of PGC information#kin the VOB pointer. In step S165, the system control unit 93 initializesthe block pointer by setting the first logical block in VOB#i indicatedby the VOB pointer in the block pointer. Next, in step S166, a check isperformed to see whether an event has been caused by a user operation,and if not, in step S167, the mechanism control unit 83 and the signalprocessing unit 84 are activated to read the logical block indicated bythe block pointer. Here, since each VOB is made up of a plurality of VOBunits which each have a management information pack at the front, amanagement information pack is read first by the signal processing unit84. The signal processing unit subjects the signal read by the opticalpickup to the variety of processes described above, and the processeddata is stored in logical block units in the buffer memory inside thesystem control unit 93. The signal separating unit 86 receives the packstransmitted from the buffer memory and refers to the stream ID andsubstream ID in the header of each pack to detect whether each pack is amanagement information pack. Here, detected management information packsare outputted to the system control unit 93.

The reproduction control unit 72 sets the transfer rate and buffer sizeincluded in each management information pack and prepares for thedecoding of the video pack, audio pack, and sub-picture pack whichfollow the management information pack in question.

Next, in step S168, the reproduction control unit 72 judges whether theblock pointer is indicating the final logical block in VOB#i, and ifnot, the processing advances to step S169, where the variable j isincremented by one, and to step S170, where the block pointer is updatedto the jth logical block in VOB#i. After this, the processing returns tostep S166 in FIG. 24C.

By repeating the processing in steps S166 to S170, all of the videopacks, audio packs, and sub-picture packs which compose the present VOBare successively read. The signal processing unit 84 performs the statedprocessing for the signal read by the optical pickup and stores the datain logical block units in the buffer memory inside the system controlunit 93. The signal processing unit 86 receives the packs sent from thebuffer memory and determines the stream ID and substream ID in theheader of each pack.

For video packs, the MPEG decoder 120 judges whether the stream ID is"1110 0000" and outputs the packs to the video decoder 87. The videodecoder 87 decodes the packs according to MPEG methods and, havingwaited an appropriate time according to the SCR and PTS, outputs thedecoded video signal to the picture mixing unit 90.

For sub-picture packs, the MPEG decoder 120 judges whether the stream IDis "1011 1101" and whether the first three bits of the substream ID are"001". The sub-picture selecting unit 122 refers to the lower-order fivebits of the sub-stream ID and judges whether the display mode indicatedin the read sub-picture pack coincides with the substream ID (CHx, MODx)indicated by the system control unit 93. This substream ID (CHx, MODx)is the substream ID, out of the sub-picture mapping information in PGCinformation #k, which coincides with the combination of the logicalchannel number (CHx) stored by the sub-picture channel register 754 andthe display mode number MODx stored by the video attribute register 755.The sub-picture selecting unit 122 discards sub-picture packs which donot have this substream ID (CHx, MODx). Here, the logical channel number(CHx) stored by the sub-picture channel register 754 and the displaymode number MODx stored by the video attribute register 755 are set inthe disc reproduction apparatus in accordance with user operations, orwith values which are set within the disc reproduction apparatus beforeshipping from the factory.

By having only the matching sub-picture packs outputted from thesub-picture selecting unit 122 to the sub-picture decoder 88, thesub-picture decoder 88 will only receive sub-picture data for thedisplay mode and the subtitle language settings which are currentlyoperational. The sub-picture decoder 88 subjects the receivedsub-picture packs to run-length decoding and waits for an appropriateperiod of time based on the SCR and the PTS before outputting the resultof the decoding to the image mixing unit 90. The outputs of the videodecoder 87 and the sub-picture decoder 88 are then mixed by the imagemixing unit 90 according to the mixing ratio specified by the systemcontrol unit 93. This mixed signal is converted into an analog signaland is outputted to the wide-screen TV monitor 2 or the standard TVmonitor 3.

When the above processing has been repeated a number of times, the blockpointer ends up indicating the final logical block in the VOB indicatedby the VOB pointer. When this is the case, the judgment "Yes" is givenin step S168, and the processing advances to step S151, where it isjudged whether the VOB pointer is indicating the final VOB in the VOBposition information table for PGC information #k. If this is not thecase, in step S152 the variable i is incremented and in step S153 theVOB pointer is set to indicate the next VOB in the VOB positioninformation of PGC#k. The processing then returns to step S165 and theprocessing in steps S166 to S170 is repeated for the newly indicatedVOB.

By repeating the above processing, the VOB pointer will end upindicating the final VOB in the VOB position information table of PGCinformation #k, with this being detected in step S151. If the VOBpointer indicates the final VOB in a VOB position information table,this means that the reproduction route indicated by one set of PGCinformation has been completed. Once a reproduction route has beencompleted, a check is performed to see if a post-processing command ispresent in the command field of the PGC information stored in the PGCinformation buffer 75. When such a command is present, the branchdestination PGC information #k is set according to the post-processingcommand in step S157, while if no command is present, the branchdestination PGC information #k is set in step S159 according to the PGClink information. After the branch destination PGC information #k hasbeen set, a recurrent call of the route processing routine is performed.

The following is an explanation of the case when the user presses the"switch display mode" key 915 during the repeated retrieval of VOBs insteps S166-S170 in the flowchart of FIG. 24C. When the "switch displaymode" key 915 is pressed, the judgment "Yes" is given in step S166 andthe processing switches to step S174 of the flowchart in FIG. 25A. StepS174 is performed to determine whether the switch display mode key 915has been pressed, so that in the present case the judgment "Yes" isgiven and the processing advances to step S131 where the aspect ratioinformation is read from the VTS management information of VTS#i. Oncethis has been read, a determination is performed in step S132 to seewhether the read aspect information is "16:9 wide screen".

If the read aspect ratio information is "16:9 wide screen", theprocessing advances to step S133, where the display mode informationMODx stored in the video attribute register 755 is read. In step S134,the set value of the display mode information MODx is incremented, andthe incremented value is stored once again in the video attributeregister 755 to update the display mode information.

As one example, when the set value MODx of the display mode represents"wide-screen TV display mode", the updating in step S134 can update theset value MODx to a value which represents "letterbox display mode".

As another example, when the set value MODx of the display moderepresents "letterbox display mode", the updating in step S134 canupdate the set value MODx to a value which represents "pan scan displaymode".

After updating, the processing advances to step S138 where the systemdetermines whether the stored display mode MODx is pan scan displaymode, and if so, the processing advances to step S139 where the panscan/letterbox conversion unit 95 is informed of pan scan display mode,before the processing advances to step S161.

If in step S138, the read display mode MODx is not pan scan displaymode, the processing advances to step S140, where the system determineswhether the stored display mode MODx is letterbox display mode. If so,the processing advances to step S141 where the pan scan/letterboxconversion unit 95 is informed of letterbox display mode, before theprocessing advances to step S161.

In step S161, the logical channel number CHx stored by the sub-picturechannel register 754 and the display mode number MODx stored by thevideo attribute register 755 are read. In step S162, the sub-picturesubstream which has a substream ID that coincides with the combination(CHx, MODx) of the numbers read in step S161 is determined out of the 32substreams which can be included in the VOB. This is determined byreferring to the sub-picture mapping information of PGC information#kwhich is stored in the PGC information buffer 75. When the combinednumber (CHx, MODx) is mapped onto one of the substream IDs, only thesubstream packs with this substream ID (hereinafter referred to asubstream ID (CHx, MODx) are decoded in step S163, with the sub-pictureselecting unit 122 and the sub-picture decoder 88 being instructed todiscard sub-picture packs with other substream IDs.

As described above, when the switch display mode key 915 is pressed, thedisplay mode MODx stored in the video attribute register 755 isincremented, a switching of display mode is performed by the panscan/letterbox conversion unit 95, and the sub-picture data to bedecoded is selected in accordance with the newly set display mode. Bydoing so, even if the user requests a switching of display mode duringthe reproduction of a video title, the sub-picture data which includes adisplay command that sets the superimposing position for the new displaymode will be selected.

The following is an explanation of the case when the user presses the"switch sub-picture channel" key 914 during the repeated retrieval ofVOBs in steps S166-S170 in the flowchart of FIG. 24C. When the "switchsub-picture channel" key 914 is pressed, the judgment "Yes" is given instep S166 and the processing switches to step S174 of the flowchart inFIG. 25A. Step S174 is performed to determine whether the switch displaymode key 915 has been pressed, so that in the present case the judgment"No"0 is given and the processing advances to step S175. In step S175,it is determined whether the switch sub-picture key 914 has beenpressed, so that in the present case the judgment "Yes" is given and theprocessing advances to step S176. In step S176, the logical channelnumber CHx stored in the sub-picture channel register 754 is read and isincremented. Next, in step S133, the display mode information MODxstored in the video attribute register 755 is read. In step S162, thesub-picture substream which has a substream ID that coincides with thecombination (CHx, MODx) of the read numbers is determined out of the 32possible substreams which can be included in the VOB. This is determinedby referring to the sub-picture mapping information of PGC information#kwhich is stored in the PGC information buffer 75. When the combinednumber (CHx, MODx) is mapped onto one of the substream IDs, only thesubstream packs with this substream ID (hereinafter referred to asubstream ID (CHx, MODx) are decoded in step S163, with the sub-pictureselecting unit 122 and the sub-picture decoder 88 being instructed todiscard sub-picture packs with other substream IDs. In step S177, theincremented channel number (CHx) is stored once again in the sub-picturechannel register 754.

As described above, when the switch sub-picture channel key 914 ispressed, the logical channel number stored in the sub-picture channelregister 754 is incremented, a switching of the logical channel numberis performed by the pan scan/letterbox conversion unit 95, and thesub-picture data to be decoded is selected in accordance with the newlyset channel number. By doing so, even if the user requests a switchingof display language of subtitles during the reproduction of a videotitle, the sub-picture data which includes a display command that setsthe superimposing position for the new display language will beselected.

FIGS. 27A to 27D show the combined images given by combining the mainimage and the sub-picture in the four display types shown in FIG. 20.

For the first display type which corresponds to the case when the aspectratio of the screen is 16:9 and the video materials have been adaptedfor wide-screen display, the DVD player 1 superimposes the Englishsubtitles "Penguin" at the superimposing position (Xw1, Yw1) to (Xw2,Yw2) shown in FIG. 13C which is unique to wide-screen TV display mode.As can be seen from FIGS. 27A and 27C, the subtitles are superimposed ata position in wide-screen TV display mode which protrudes into the areatrimmed in pan scan display mode. This sub-picture unit displayed inwide-screen TV display mode can therefore be seen to make full use ofthe width of a wide-screen TV and is superimposed at the position shownin FIG. 27A.

For the second display type which corresponds to the case when thedisplay mode is "4:3 letterbox" and the video materials have beenadapted for wide-screen display, the DVD player 1 superimposes theEnglish subtitles "Penguin" at the superimposing position (Xb1, Yb1) to(Xb2, Yb2) shown in FIG. 13B which is unique to letterbox display mode.As shown in FIG. 13B, the subtitles "Penguin" are superimposed at aposition which is neatly positioned over the corrective image. Bysetting the superimposing position of RLE code sequence f11 in this way,the subtitles can be displayed in letterbox display mode at a positionwhich does not overlap the main image, with this being shown in FIG.27B.

For the third display type which corresponds to the case when thedisplay mode is "4:3 pan scan" and the video materials have been adaptedfor wide-screen display, the DVD player 1 superimposes the Englishsubtitles "Penguin" at the superimposing position (Xp1, Yp1) to (Xp2,Yp2) shown in FIG. 13A which is unique to pan scan display mode. Asshown in FIG. 13A, the subtitles have been superimposed at a positionwhich has been shifted somewhat to the left so as to not protrude intothe trimmed area. As a result, the subtitles do not end up being trimmedand so can be properly displayed, as shown in FIG. 27C.

For the fourth display type which corresponds to the case when theaspect ratio of the screen is 4:3 and the video materials have not beenadapted for wide-screen display, DVD player 1 superimposes the Englishsubtitles "Big Fish" as shown in FIG. 27D.

With the present embodiment of the invention described above, amultimedia optical disc can be achieved where information for theselection of sub-picture information, in accordance with the settings ofdisplay mode and sub-picture channel number, is stored for each unit ofPGC information. As a result, a disc reproduction apparatus can changethe substream ID by which the selection of sub-picture information ismade for every PGC information unit.

As one example, in one set of PGC information, the substream ID#1 canrepresent English subtitles and letterbox display mode, substream ID#2can represent English subtitles and pan scan display mode, and substreamID#3 can represent English subtitles and wide-screen TV display mode.Even so, in a different set of PGC information, all display modes can beset at, say, substream ID#2 by changing the sub-picture mappinginformation in the PGC information. This corresponds to the case wherethe subtitles are centered on the screen and so are largely unaffectedby the selected display mode. As a result, all display modes may use thesame substream.

The present invention has been described in terms of one specificembodiment, although it should be obvious that several modifications arepossible within its scope, provided they are still relate to a systemwhich avoids the displacement of a sub-picture when switching displaymode. Examples of possible modifications are given below. (a) Thepresent embodiment describes the case where a digital video disc (DVD)is used as the multimedia optical disc, although any other type ofrecording media which can store a plurality of sub-pictures multiplexedwith video data may be used. The reproduction device is also describedas reproducing a DVD, although so long as it receives information inwhich a plurality of sub-pictures are multiplexed with videoinformation, this need not be the case. The reproduction device mayinstead include a reception means for receiving data communication. Anexample of this communication would be a digital broadcast of a MPEGstream using satellite broadcasting. Here, frequency multiplexing andtime axis multiplexing are available as methods for transmitting aplurality of MPEG streams to allow selective reproduction. In the timeaxis multiplexing method, selective reproduction is performed by waitingfor the broadcast of the selected MPEG stream and reproducing the streamwhen it is transferred.

(b) In the present embodiment, all video materials which are adapted towide-screen display mode are described as having the potential to bedisplayed in pan scan display mode or letterbox display mode, althoughin reality, there are cases where the video content is unsuited totrimming or reduction, making it necessary to clarify such limitations.To overcome this problem, "display mode information", which showswhether letterbox or pan scan display modes are available, can beincluded in the video title set management information to prevent theuser from selecting letterbox or pan scan display mode whereinappropriate.

(c) The VOB position information table of the present invention has beendescribed as a list of storage locations for VOBs, based on which thedisc reproduction apparatus reads VOBs, although by storing partialareas of the storage locations of the VOBs in this table, the opticalpickup can be made to read only part of the VOBs, such partial readingbeing known as "trimming". These trimmed parts of VOBs are indicated inunits called cells. By doing so, by indicating partial areas in the VOBposition information, only part of a VOB is used as a core part, so thatan increase in the efficiency with which video materials are used can bemade.

(d) In the present embodiment, the subtitles are described as beingcomposed of image data, although it is equally possible for thesub-picture to be composed of vector graphics, or three-dimensionalcomputer graphics (CG). By doing so, games which use compressed videofootage and computer graphics can be achieved using the present disc.

(e) In the present embodiment, a VOB unit consists of one GOP, althoughit should be needless to say that if the stored video information has areproduction time of about one second, a VOB unit may consist of two orthree GOPs with a very short reproduction time. In this case, onemanagement information pack is set before such a plurality ofconsecutive GOPs. The management information pack is then effective forthe plurality of GOPs.

(f) In the present embodiment, PCM data and AC-3 data are used as theaudio data, although any other format which may be interleaved into asystem stream may be used, with examples of such being compressed PCM,MPEG audio data, and MIDI data.

(g) In the present embodiment, digital moving picture data according toMPEG2 standard is used for the moving picture data. However, other kindsof moving picture data, such as the digital moving picture data underMPEG1 or digital moving picture data with a conversion algorithm otherthan DCT (Discrete Cosine Transform) under MPEG, may be used so long asthe moving picture data can be combined with audio data and sub-picturedata to form multimedia data.

(h) In the present embodiment, management information packs are includedin VOBUs in units of GOPs, these being the units of reproducing movingpicture data. However, it should be obvious that if the method forcompressing digital moving pictures changes, the unit of the managementinformation pack changes according to the compression method.

Finally, a method for producing the optical disc used in the presentembodiment is described. The editor prepares master tapes, such as videotapes of various shots filmed with video cameras and music tapes inwhich songs and sounds are recorded live. The moving pictures and soundsin the tapes are digitized and loaded into a nonlinear editing machine.The editor creates menus and items using application programs, such as agraphic editor provided in an editing machine, and reproduces video andsounds frame by frame. The editor also creates management informationpacks including Highlight commands using a GUI generator or the like.The editor then encodes the above data according to MPEG standards tocreate video data, audio data, sub-picture data, and managementinformation packs. After this, the editor creates VOB units and VOBsusing the nonlinear editing machine. The editor also assigns numbers tothe VOBs. Also, the editor creates PGC information #1, #2, #3, . . . ,#n, a VM title search pointer table, and a video manager. The editorthen loads these sets of data into the memory of a workstation.

The data is converted into logical data sequences so that the data isrecorded in the file area. The logical data sequences are recorded ontoa medium, such as the magnetic tape, then converted to physical datasequences. The physical data sequences include volume data with ECC(Error Check Code), Eight-to-Sixteen conversion, and data in the lead-inarea and lead-out area. A master optical disc is produced using thephysical data sequences. Then, copies of the master optical disc aremanufactured by using a pressing machine.

Conventional CD manufacturing machines may be used for manufacturing theabove-constructed optical disc with the exception of the processesrelated to the generation of logical data sequences for the dataconstruction of the present invention. These manufacturing methods aredescribed in Heitaro Nakajima and Hiroji Ogawa: "Compact Disc Dokuhon",Ohmu Ltd. and Applied Physics Society Optics Meeting: Optical DiscSystem, Asakura Shoten.

Commercial Applications

The multimedia optical disc of the present invention stores high impactwide-screen TV video titles and allows the favorable distribution andretailing of such optical titles.

The reproduction apparatus and method of the present invention allow thereproduction of the above disc by low cost household AV equipment withlimited memory capacity.

Although the present invention has been fully described by way ofexamples with reference to the accompanying drawings, it is to be notedthat various changes and modifications will be apparent to those skilledin the art. Therefore, unless such changes and modifications depart fromthe scope of the present invention, they should be construed as beingincluded therein.

What is claimed is:
 1. An optical disc having recorded thereon mainvideo data which is composed of a sequence of a plurality of sets offrame data, each set of frame data being processed beforehand to enabledisplay at an aspect ratio specified out of a plurality of aspectratios, wherein the optical disc comprises:a stream area in whichstreams are made up of video objects, including video objects havingmain video data and a plurality of sets of sub-picture data, whereineach set of sub-picture data includes a set of tel-op data and a set ofcoordinate information showing a display position of the set of tel-opdata; and a control area in which a plurality of pairings of a set ofdisplay mode information and a set of sub-picture indicating informationare recorded to enable a plurality of display methods; wherein each setof display mode information enables the frame data to be decoded fromthe main video data and displayed by one of the display methods at oneof the plurality of aspect ratios, and wherein each set of thesub-picture indicating information shows a set of sub-picture data, outof the plurality of sets of sub-picture data in the same stream as themain video data, which includes a set of coordinate information whichcoincides with one of the display methods shown by the display modeinformation.
 2. The optical disc of claim 1 wherein the plurality ofaspect ratios includes 4:3 and 16:9, and wherein the frame data isprocessed according to one of the following species of display methods;awide-screen television mode in which images with an aspect ratio of 16:9are displayed on a display screen with an aspect ratio of 16:9; astandard television mode in which images with an aspect ratio of 4:3 aredisplayed on a display screen with an aspect ratio of 4:3; a pan scanmode in which images with an aspect ratio of 16:9 are displayed on adisplay screen with an aspect ratio of 4:3, after trimming, to give 4:3aspect ratio images; and a letterbox display mode in which images withan aspect ratio of 16:9 are displayed on a display screen with an aspectratio of 4:3 after processing to add corrective images.
 3. The opticaldisc of claim 2 wherein each set of sub-picture data includes at leastone of the following types of coordinate information:a wide screentelevision mode coordinate information for setting a display modeposition of tel-op data when the frame data is processed according tothe wide-screen television mode; a standard television mode coordinateinformation for setting a display position of tel-op data in acoordinate system for display according to the standard television mode;a pan scan mode coordinate information for setting a display position oftel-op data in a coordinate system for display according to the pan scanmode; and a letterbox mode coordinate information for setting a displayposition of tel-op data in a coordinate system for display according tothe letterbox mode, and wherein the control area is arranged such thatthe sub-picture indicating information which indicates a set ofsub-picture data that includes the wide-screen television modecoordinate information is paired with display mode information whichshows the wide-screen television mode, the sub-picture indicatinginformation which indicates a set of sub-picture data that includes thestandard television mode coordinate information is paired with thedisplay mode information which shows the standard television mode, thesub-picture indicating information which indicates a set of sub-picturedata that includes the pan scan mode coordinate information is pairedwith the display mode information which shows the pan scan mode, and thesub-picture indicating information which indicates a set of sub-picturedata that includes the letterbox mode coordinate information is pairedwith the display mode information which shows the letterbox mode.
 4. Areproduction system comprising an optical disc, wherein the optical dischas:a stream area in which streams are made up of video objects,including video objects having main video data, which is an arrangementof a plurality of sets of frame data which has been processed to enabledisplay at an aspect ratio specified out of a plurality of aspectratios, and a plurality of sets of sub-picture data, which each includea set of tel-op data and a set of coordinate information for a displayposition of the set of tel-op data; and a control area which includes aplurality of pairings of display mode information, each of which enablesprocessing frame data, which has been decoded from the main video datain a stream, for display at one of the plurality of aspect ratios, andsub-picture data indicating information which indicates one of the setof sub-picture data, out of the plurality of sets of sub-picture dataincluded in a same stream as the main video image, which includes thecoordinate information that corresponds to one of the display modeinformation, and a reproduction apparatus comprising:an optical pickupfor optically reading data from the optical disc; a drive mechanism fordriving the optical pickup; first controlling means for controlling thedrive mechanism to have the optical pickup read data from the controlarea of the optical disc; a buffer for storing at least one set of thedisplay mode information and one set of the sub-picture indicatinginformation included in the data read according to the control by thefirst controlling means; second controlling means for controlling thedrive mechanism to have the optical pickup read a stream from theoptical disc; a display setting register for storing display styleinformation indicating a species of display methods by which frame datais to be processed; a video decoder for decoding main video dataincluded in the stream read from the optical disc into frame data;determining means for referring to the sets of display mode informationincluded in the data stored in the buffer and for determining thesub-picture indicating information which coincides with the displaystyle information stored in the display setting register; a sub-picturedecoder for decoding a set of sub-picture data indicated by thedetermined sub-picture indicating information into a set of tel-op data,out of a plurality of the sets of sub-picture data included in thestream read from the optical disc; processing means for processingimages of frame data, based on the display style information stored inthe display setting register; and combining means for arranging thedecoded set of tel-op data onto the processed images of frame data inaccordance with the coordinate information included in a set ofsub-picture data and for combining the tel-op data and processed images.5. The reproduction apparatus of claim 4, wherein the display styleinformation stored in the display setting register is an indication forone of a wide-screen television mode, a standard television mode, a panscan display mode, and a letterbox display mode, and wherein theprocessing means includes:a pan scan conversion unit for converting,when the display style information stored in the display settingregister is an indication for the pan scan display mode, images of theframe data decoded by the video decoder into images with an aspect ratioof 16:9, before trimming the converted images to give images with anaspect ratio of 4:3; and a letterbox conversion unit for converting,when the display style information stored in the display settingregister is an indication for the letterbox display mode, images of theframe data decoded by the video decoder into images with an aspect ratioof 16:9, before adding a corrective image to the converted images togive images with an aspect ratio of 4:3.
 6. The disc reproductionapparatus of claim 5, further including:receiving means for receiving auser setting of the display style information; and an updating means forupdating the display style setting of display style information in thedisplay setting register, when the receiving means has received a usersetting for the display style information.
 7. A reproduction method forreproducing streams of data from a storage medium, wherein the streamsare composed of video objects including main image data which is anarrangement of frame data which has been processed to allow display bydisplay screens of a plurality of aspect ratios, and sets of sub-picturedata which each include a set of tel-op data and a set of coordinateinformation for a display position of the set of tel-op data, comprisingthe step of:using display mode information that shows a species ofdisplay methods for processing frame data, which has been decoded fromthe main video data in a stream, for display at one of the plurality ofaspect ratios and sub-picture indicating information which indicates oneset of sub-picture data, out of a plurality of sets of sub-picture dataincluded in a same stream as the main video image, which includescoordinate information that corresponds to the species shown by thedisplay mode information, the reproduction method further including:aretrieving step for retrieving a plurality of combinations of displaymode information and sub-picture indicating information; a receivingstep for receiving a user indication of display style informationindicating one of the species of display methods to be used to processthe frame data; a video-decoding step for decoding the main video dataincluded in a retrieved stream into frame data; a determining step forreferring to the plurality of sets of display mode information retrievedin the retrieving step and for determining a set of sub-pictureindicating information which coincides with the display styleinformation received in the receiving step; a sub-picture decoding stepfor decoding the set of sub-picture data indicated by the set ofsub-picture indicating information, out of the sets of sub-picture dataincluded in the retrieved streams; a processing step for processingimages of frame data based on the display style information stored inthe display setting register; and a combining step for arranging thedecoded set of tel-op data onto the processed images of frame data inaccordance with the coordinate information included in the set ofsub-picture data and for combining the tel-op data and the processedimages.